Installer GUI locks up when help window is opened after pressing next...and MOK fails

[thomasadelhardt]

During installation of Linux Mint with Secure Boot enabled, the installer GUI becomes stuck in a state where the help window remains permanently in focus. This prevents the user from completing the installation. After forced reboot, the system fails to boot.

Steps to reproduce

1. Boot Linux Mint installer with Secure Boot enabled in BIOS.
2. Start installation normally.
3. Reach the step where the installer asks the user to note down the Secure Boot MOK password (the one required after reboot).
4. Click Next.
5. Before the installer proceeds to next screen then press the help button (question mark icon).
6. A help window opens.
7. The installer proceeds to the next screen, but the help window stays open on top.
8. The help window cannot be closed, and it steals focus permanently, blocking all interaction with the installer.
9. User is forced to reboot.
10. After reboot, the system fails to boot, with this error:
    Failed to open \EFI\BOOT\mmx64.efi - not found
    Failed to load image ###: Not found
    Failed to start MokManager: Not Found
    Something has gone seriously wrong: import_mok_state() failed: Not Found