Navigation Polygon Breaks After Re-baked on Godot Engine v4.3

[bac0id]

Which demo project is affected:

• Navigation Polygon 2D, downloaded from https://godotengine.org/asset-library/asset/2722

OS/device including version:

• Godot Engine: v4.3.stable.mono.official [77dcf97d8]
• OS: Windows 10 x64

Issue description:

• Project is upgraded from 4.2 to 4.3.
• At the first launch, navigation works well. Navigation Polygon looks right.
• After I click "Bake Navigation Polygon" on toolbar, newer Navigation Polygon looks weird. And navigation becomes weird too.
• Debugger shows following info:

E 0:00:03:0247   sync: Navigation map synchronization error. Attempted to merge a navigation mesh polygon edge with another already-merged edge. This is usually caused by crossing edges, overlapping polygons, or a mismatch of the NavigationMesh / NavigationPolygon baked 'cell_size' and navigation map 'cell_size'. If you're certain none of above is the case, change 'navigation/3d/merge_rasterizer_cell_scale' to 0.001.
  <C++ source>      modules/navigation/nav_map.cpp:990 @ sync()

Screenshots of issue:

[smix8]

Navmesh baking for 2D did not exist when this demo was made, the baking was added in 4.3.

The demo uses a custom hand-crafted navmesh that is gone as soon as you try to bake something because there is no valid bake geometry.

The reason it still has this somehow broken pathfinding after the bake is because the NavigationPolygon has old nested outline data stored but half of the inner outlines are winded in the wrong direction so need to be redone.

EDIT

Made a PR to fix the demo #1135