New CPU Lightmapper crashes with GridMap when baking

[DarkKilauea]

Godot version:

Godot Engine v3.2.4.beta5+lightmapper.official

OS/device including version:

Windows 10 (Build: 19042.685, Arch: x64)
AMD Ryzen 7 3800XT
NVidia GeForce RTX 2080 (running GLES3)

Issue description:

I was testing the new CPU lightmapper proposed in #44628 with a simple GridMap. Whenever I try to bake the lightmap for the scene, I get a crash. Sample scene is attached.

Log:

Godot Engine v3.2.4.beta5+lightmapper.official - https://godotengine.org
OpenGL ES 3.0 Renderer: GeForce RTX 2080/PCIe/SSE2
OpenGL ES Batching: ON

ERROR: get: FATAL: Index p_index = 0 is out of bounds (size() = 0).
   At: ./core/cowdata.h:152

I tested the same scene with the official build of v3.2.4.beta5 and the lightmapper worked fine there.

Steps to reproduce:

1. Create a scene and add a Gridmap.
2. Create a MeshLibrary containing a cube as the only item.
3. Paint a scene with the cube "tiles",
4. Add some lights.
5. Add a BakedLightmap node and cover the GridMap in its extents.
6. Click the "Bake" button.

Minimal reproduction project:

TestGridmapLightmap.zip

[JFonS]

It was a simple error from my side, I already found a fix for it, but I'm waiting to update the PR together with some other fixes. I will keep you posted :)

[DarkKilauea]

Confirming that the issue is fixed in 3.2.4 beta 6.