Bug reporter wrapped inside GTK window, showing GTK titlebar and borders

Reproduction steps:
1. Create a new project
2. Click Help > Report a Bug

Expected results: only one title bar exists for the bug reporter window
Actual results: Bug reporter window is inside another GTK window, showing two title bars

Reproduced with: 6000.1.0a10, 6000.1.0b4, 6000.2.0a1
Not reproduced with: 2022.3.57f1, 6000.0.36f1, 6000.1.0a9

Reproduced on: Ubuntu 24.04
Not reproduced on: no other environment tested