Qubes updater 4.2.1 crashes at start (index out of range)

My Qubes Update gui app will not start (did before). Get the following errors in dom0 command line:

[alpha@dom0 ~]$ qubes-update-gui --log DEBUG
Traceback (most recent call last):
  File "/usr/lib/python3.11/site-packages/qui/updater/updater.py", line 58, in do_activate
    self.perform_setup()
  File "/usr/lib/python3.11/site-packages/qui/updater/updater.py", line 155, in perform_setup
    self.intro_page.populate_vm_list(self.qapp, self.settings)
  File "/usr/lib/python3.11/site-packages/qui/updater/intro_page.py", line 106, in populate_vm_list
    self.refresh_update_list(settings.update_if_stale)
  File "/usr/lib/python3.11/site-packages/qui/updater/intro_page.py", line 122, in refresh_update_list
    in output.decode().split("\n", maxsplit=1)[0]
       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
IndexError: list index out of range
Traceback (most recent call last):
  File "/usr/lib/python3.11/site-packages/qui/updater/updater.py", line 58, in do_activate
    self.perform_setup()
  File "/usr/lib/python3.11/site-packages/qui/updater/updater.py", line 155, in perform_setup
    self.intro_page.populate_vm_list(self.qapp, self.settings)
  File "/usr/lib/python3.11/site-packages/qui/updater/intro_page.py", line 106, in populate_vm_list
    self.refresh_update_list(settings.update_if_stale)
  File "/usr/lib/python3.11/site-packages/qui/updater/intro_page.py", line 122, in refresh_update_list
    in output.decode().split("\n", maxsplit=1)[0]
       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
IndexError: list index out of range

These are my qubes:

[alpha@dom0 ~]$ qvm-volume
POOL:VOLUME                                               VMNAME                     VOLUME_NAME  REVERT_POSSIBLE
linux-kernel:6.6.29-1.fc37                                work                       kernel       No
                                                          anon-whonix                kernel       No
                                                          calc-only-whonix           kernel       No
                                                          crypto-ML-nordvpn          kernel       No
                                                          crypto-nordvpn             kernel       No
                                                          crypto-whonix              kernel       No
                                                          debian-12-unof-repos       kernel       No
                                                          debian-12-xfce             kernel       No
                                                          default-dvm                kernel       No
                                                          default-mgmt-dvm           kernel       No
                                                          fedora-39-sys              kernel       No
                                                          fedora-39-sys-dvm          kernel       No
                                                          fedora-39-xfce             kernel       No
                                                          sys-firewall               kernel       No
                                                          sys-net                    kernel       No
                                                          sys-usb                    kernel       No
                                                          sys-whonix                 kernel       No
                                                          vault-nonet                kernel       No
                                                          whonix-gateway-17          kernel       No
                                                          whonix-workstation-17      kernel       No
                                                          whonix-workstation-17-dvm  kernel       No
vm-pool:qubes_dom0/vm-anon-whonix-private                 anon-whonix                private      Yes
vm-pool:qubes_dom0/vm-anon-whonix-root                    anon-whonix                root         No
vm-pool:qubes_dom0/vm-anon-whonix-volatile                anon-whonix                volatile     No
vm-pool:qubes_dom0/vm-calc-only-whonix-private            calc-only-whonix           private      Yes
vm-pool:qubes_dom0/vm-calc-only-whonix-root               calc-only-whonix           root         No
vm-pool:qubes_dom0/vm-calc-only-whonix-volatile           calc-only-whonix           volatile     No
vm-pool:qubes_dom0/vm-crypto-ML-nordvpn-private           crypto-ML-nordvpn          private      Yes
vm-pool:qubes_dom0/vm-crypto-ML-nordvpn-root              crypto-ML-nordvpn          root         No
vm-pool:qubes_dom0/vm-crypto-ML-nordvpn-volatile          crypto-ML-nordvpn          volatile     No
vm-pool:qubes_dom0/vm-crypto-nordvpn-private              crypto-nordvpn             private      Yes
vm-pool:qubes_dom0/vm-crypto-nordvpn-root                 crypto-nordvpn             root         No
vm-pool:qubes_dom0/vm-crypto-nordvpn-volatile             crypto-nordvpn             volatile     No
vm-pool:qubes_dom0/vm-crypto-whonix-private               crypto-whonix              private      Yes
vm-pool:qubes_dom0/vm-crypto-whonix-root                  crypto-whonix              root         No
vm-pool:qubes_dom0/vm-crypto-whonix-volatile              crypto-whonix              volatile     No
vm-pool:qubes_dom0/vm-debian-12-unof-repos-private        debian-12-unof-repos       private      Yes
vm-pool:qubes_dom0/vm-debian-12-unof-repos-root           debian-12-unof-repos       root         Yes
vm-pool:qubes_dom0/vm-debian-12-unof-repos-volatile       debian-12-unof-repos       volatile     No
vm-pool:qubes_dom0/vm-debian-12-xfce-private              debian-12-xfce             private      Yes
vm-pool:qubes_dom0/vm-debian-12-xfce-root                 debian-12-xfce             root         Yes
vm-pool:qubes_dom0/vm-debian-12-xfce-volatile             debian-12-xfce             volatile     No
vm-pool:qubes_dom0/vm-default-dvm-private                 default-dvm                private      No
vm-pool:qubes_dom0/vm-default-dvm-root                    default-dvm                root         No
vm-pool:qubes_dom0/vm-default-dvm-volatile                default-dvm                volatile     No
vm-pool:qubes_dom0/vm-default-mgmt-dvm-private            default-mgmt-dvm           private      No
vm-pool:qubes_dom0/vm-default-mgmt-dvm-root               default-mgmt-dvm           root         No
vm-pool:qubes_dom0/vm-default-mgmt-dvm-volatile           default-mgmt-dvm           volatile     No
vm-pool:qubes_dom0/vm-fedora-39-sys-dvm-private           fedora-39-sys-dvm          private      Yes
vm-pool:qubes_dom0/vm-fedora-39-sys-dvm-root              fedora-39-sys-dvm          root         No
vm-pool:qubes_dom0/vm-fedora-39-sys-dvm-volatile          fedora-39-sys-dvm          volatile     No
vm-pool:qubes_dom0/vm-fedora-39-sys-private               fedora-39-sys              private      Yes
vm-pool:qubes_dom0/vm-fedora-39-sys-root                  fedora-39-sys              root         Yes
vm-pool:qubes_dom0/vm-fedora-39-sys-volatile              fedora-39-sys              volatile     No
vm-pool:qubes_dom0/vm-fedora-39-xfce-private              fedora-39-xfce             private      Yes
vm-pool:qubes_dom0/vm-fedora-39-xfce-root                 fedora-39-xfce             root         Yes
vm-pool:qubes_dom0/vm-fedora-39-xfce-volatile             fedora-39-xfce             volatile     No
vm-pool:qubes_dom0/vm-sys-firewall-private                sys-firewall               private      No
vm-pool:qubes_dom0/vm-sys-firewall-root                   sys-firewall               root         No
vm-pool:qubes_dom0/vm-sys-firewall-volatile               sys-firewall               volatile     No
vm-pool:qubes_dom0/vm-sys-net-private                     sys-net                    private      Yes
vm-pool:qubes_dom0/vm-sys-net-root                        sys-net                    root         No
vm-pool:qubes_dom0/vm-sys-net-volatile                    sys-net                    volatile     No
vm-pool:qubes_dom0/vm-sys-usb-private                     sys-usb                    private      No
vm-pool:qubes_dom0/vm-sys-usb-root                        sys-usb                    root         No
vm-pool:qubes_dom0/vm-sys-usb-volatile                    sys-usb                    volatile     No
vm-pool:qubes_dom0/vm-sys-whonix-private                  sys-whonix                 private      Yes
vm-pool:qubes_dom0/vm-sys-whonix-root                     sys-whonix                 root         No
vm-pool:qubes_dom0/vm-sys-whonix-volatile                 sys-whonix                 volatile     No
vm-pool:qubes_dom0/vm-vault-nonet-private                 vault-nonet                private      Yes
vm-pool:qubes_dom0/vm-vault-nonet-root                    vault-nonet                root         No
vm-pool:qubes_dom0/vm-vault-nonet-volatile                vault-nonet                volatile     No
vm-pool:qubes_dom0/vm-whonix-gateway-17-private           whonix-gateway-17          private      Yes
vm-pool:qubes_dom0/vm-whonix-gateway-17-root              whonix-gateway-17          root         Yes
vm-pool:qubes_dom0/vm-whonix-gateway-17-volatile          whonix-gateway-17          volatile     No
vm-pool:qubes_dom0/vm-whonix-workstation-17-dvm-private   whonix-workstation-17-dvm  private      No
vm-pool:qubes_dom0/vm-whonix-workstation-17-dvm-root      whonix-workstation-17-dvm  root         No
vm-pool:qubes_dom0/vm-whonix-workstation-17-dvm-volatile  whonix-workstation-17-dvm  volatile     No
vm-pool:qubes_dom0/vm-whonix-workstation-17-private       whonix-workstation-17      private      Yes
vm-pool:qubes_dom0/vm-whonix-workstation-17-root          whonix-workstation-17      root         Yes
vm-pool:qubes_dom0/vm-whonix-workstation-17-volatile      whonix-workstation-17      volatile     No
vm-pool:qubes_dom0/vm-work-private                        work                       private      Yes
vm-pool:qubes_dom0/vm-work-root                           work                       root         No
vm-pool:qubes_dom0/vm-work-volatile                       work                       volatile     No

Thank you. Unfortunately I cannot implement the fix described (changes to /usr/lib/python3.11/site-packages/qui/updater/intro_page.py), as my intro_page.py looks quite different.

Have added a comment describing it here: Qubes-update-gui doesn't start (crashes) after updating to 4.2 · Issue #9203 · QubesOS/qubes-issues · GitHub