Node LightmapGI causing a crash on the mobile version of Godot Engine.

### Tested versions

Tested on versions v4.6.0 to v4.6.2, both "stable".

### System information

Godot Engine v4.6.2.stable.official.71f334935 - https://godotengine.org OpenGL API OpenGL ES 3.2 V@0615.80 (GIT@406382a20f, I986008d073, 1704447428) (Date:01/05/24) - Compatibility - Using Device: Qualcomm - Adreno (TM) 710

### Issue description

It’s hard to explain, but basically I built a scene using Gridmap3D and added some lights once I was sure the scene was finished, setting all the lights to static. Then I added LightmapGI to the scene and clicked “Bake.” As expected, it froze for a few seconds since it’s very demanding on the hardware, but it had never happened before that the node would crash the program. I tested it on simpler scenes and the bake worked normally, although the system would still freeze during the bake, which is expected.

I’m not sure if the issue is related to compatibility mode (OpenGL), but right now I’m unable to add lighting to my project because LightmapGI is crashing the engine. Note: the “.exr” file doesn’t even get created, so it might be crashing before LightmapGI even starts calculating anything.

### Steps to reproduce

I built a scene using Gridmap3D and tried to bake it. All the meshes in tile format already have UVs for the Lightmap.

### Minimal reproduction project (MRP)

[LightmapGI_Crash.zip](https://github.com/user-attachments/files/26484190/LightmapGI_Crash.zip)

Start by running the attached LightmapGI_Crash.zip reproduction on Godot v4.6.0–v4.6.2 in Compatibility/OpenGL on the listed Qualcomm Adreno 710 device, then compare it with a simpler scene where baking succeeds. Trace the LightmapGI bake path for the Gridmap3D scene and verify that baking completes without crashing and creates the expected .exr file.

Written by the indexing model from the issue text.