Linux Desktop becomes unresponsive when switching to file tab in multi-page view

[Quwex]

The Linux Desktop app hangs when switching notebookbar tabs from right to left, specifically when reaching the File tab when multi-page view is enabled.

Reported originally by @mmeeks on #cool-dev:matrix.org

Steps to Reproduce

1. Launch the app and select Blank Document (Writer)
2. Switch to multi-page view (via bottom toolbar icon)
3. Insert four page breaks with Ctrl+Enter, type some text on each page
4. Switch between notebookbar tabs from right to left arriving at the File tab.
5. When clicking the File tab, the app becomes unresponsive

Expected Behavior

Switching to the File tab should show the File menu/backstage view without hanging.

Actual Behavior

The app freezes and becomes completely unresponsive upon clicking the File tab.

• Version: 26.04.0.1 (git hash: 33527a8)