bug:Scene viewport goes blank after re-docking a floated scene editor

Release Type: Official Release

Version: 4.4.0-beta6

Platform(s): Windows 11 (build 26200), x64

Describe the bug

When a scene editor document is undocked into a floating window and then docked
back into the main Game Studio window, the 3D viewport stops rendering. The
panel is still laid out in the dock and still receives the usual chrome, but
the scene content never comes back.

The first direction works correctly: dragging the scene document out of Game
Studio into a floating window keeps the viewport rendering normally. Only the
return trip breaks it.

To Reproduce

1. Open Game Studio and open any scene. The viewport renders normally.
2. Drag the scene document tab out of the main window so it becomes a floating
   window. → Viewport still renders correctly.
3. Drag the floating window back into Game Studio to re-dock it.
4. The viewport area is now blank and never resumes rendering.

Expected behavior

The viewport should resume rendering after re-docking.

Screenshots

Reproduce the blank viewport in Game Studio by floating a scene editor and re-docking it, confirming that undocking alone still renders. Start by tracing the scene editor's docking and viewport rendering lifecycle; done means the 3D scene renders again after re-docking without regressing the floating-window case.