### Godot version

0810ecaafdbee3ea747219e6ab3a8de5d2216a09

### System information

Windows 11, Nvidia 3000, firefox

### Issue description

Exporting the gltf file is corrupt in blender.

### Steps to reproduce

1. Open project.
2. Export as glb
3. Open in blender
4. Blender display many warnings

![image](https://user-images.githubusercontent.com/32321/216740742-de662c5c-f5c3-44b5-a36e-8ad33defdbba.png)


### Minimal reproduction project

https://cdn.discordapp.com/attachments/598003845657788438/1071249610896580691/Test_Game_Project.zip


if (p_state->lights.is_empty()) {
		return OK;
	}
	Array lights;
	for (GLTFLightIndex i = 0; i < p_state->lights.size(); i++) {
		lights.push_back(p_state->lights[i]->to_dictionary());
	}
	Dictionary extensions;
	if (p_state->json.has("extensions")) {
		extensions = p_state->json["extensions"];
	} else {
		p_state->json["extensions"] = extensions;
	}
	Dictionary lights_punctual;
	extensions["KHR_lights_punctual"] = lights_punctual;
	lights_punctual["lights"] = lights;
	print_verbose("glTF: Total lights: " + itos(p_state->lights.size()));
	return OK;
}
Error GLTFDocument::_serialize_cameras(Ref<GLTFState> p_state) {