"Parameter "texture" is null" error and no visible update until editor restart, when baking lightmap with Compatibility renderer on macOS

### Tested versions

Reproducible in:
- v4.7.dev.custom_build [3c5e56102]
- v4.6.stable.official [89cea1439]
- v4.5.1.stable.official [f62fdbde1]
- v4.5.stable.official [876b29033]

### System information

Godot v4.7.dev (3c5e56102) - macOS Tahoe (26.2.0) - Multi-window, 2 monitors - OpenGL 3 (Compatibility) - Apple M4 Pro - Apple M4 Pro (14 threads) - 24.00 GiB memory

### Issue description

At the end of attempting to bake a lightmap using the LightmapGI node, the Output panel prints out the following error message:
```
ERROR: ./drivers/gles3/storage/texture_storage.cpp:2235 - Parameter "texture" is null.
Done baking lightmaps in 00:00:01.07.
```
(from v4.7.dev.custom_build [3c5e56102])

It seems that if baked lighting already exists, then the new baked lighting does not appear until the editor is closed and reopened.

I'm not sure if it's relevant to this issue or it's separate, but I have noticed that when I open a project with lightmaps, I receive this warning several times:
```
WARNING: ./drivers/gles3/storage/texture_storage.cpp:985 - Image format BPTC_RGBFU not supported by hardware, converting to RGBHalf.
```
(from v4.7.dev.custom_build [3c5e56102])

Error/warning messages:

https://github.com/user-attachments/assets/ede2a159-9f4e-489c-9941-7270cb9ef29d

Not updating until restart (and error/warning messages again, I suppose):

https://github.com/user-attachments/assets/c29a9228-e18f-4682-aa12-b04cf42b4002

### Steps to reproduce

In the MRP, select the LightmapGI node and press "Bake Lightmaps". Select a file location to save the `.lmbake` file.

The scene should take a few moments to bake, and the Output console should have the following:
```
Done baking lightmaps in 00:00:00.00.
WARNING: ./drivers/gles3/storage/texture_storage.cpp:985 - Image format BPTC_RGBFU not supported by hardware, converting to RGBHalf.
WARNING: ./drivers/gles3/storage/texture_storage.cpp:985 - Image format BPTC_RGBFU not supported by hardware, converting to RGBHalf.
WARNING: ./drivers/gles3/storage/texture_storage.cpp:985 - Image format BPTC_RGBFU not supported by hardware, converting to RGBHalf.
ERROR: ./drivers/gles3/storage/texture_storage.cpp:2235 - Parameter "texture" is null.
Done baking lightmaps in 00:00:01.44.
```

Change the color of the OmniLight3D in the scene, then re-bake the lighting. Nothing will visibly change. Close and restart the editor; the change in lighting will now be visible.

### Minimal reproduction project (MRP)

[test-lightmapping_2026-02-02_21-26-54.zip](https://github.com/user-attachments/files/25031990/test-lightmapping_2026-02-02_21-26-54.zip)

Use the minimal reproduction project and bake the LightmapGI scene with the Compatibility renderer on macOS, then repeat after changing the OmniLight3D color. Start by inspecting drivers/gles3/storage/texture_storage.cpp around the reported lines and trace the lightmap bake update path. Done means the updated lighting appears without restarting the editor and the null-texture error no longer appears.

Written by the indexing model from the issue text.