### Godot version

4.0.2 stable

### System information

issue tested on win10 with ryzen 7 and rx 6600, win11 with ryzen 7 and gtx 3050

### Issue description

When creating a screen reading post processing shader, the normal buffer functions correctly in the editor, but does not seem to be functioning as expected in debug, producing only a solid colour when run. I am unsure if this behaviour is intended, but if so, I feel it should be properly documented.

Running correctly in editor:
![image](https://user-images.githubusercontent.com/71034402/230672620-fc5e4baf-c12e-4755-b7a2-206087459307.png)

Solid colour in debug:
![image](https://user-images.githubusercontent.com/71034402/230672489-d9c29755-c2d3-4e72-9ea0-355148e916fe.png)


### Steps to reproduce

*this shader should be attached to a MeshInstance3D quadmesh*
minimal shader to reproduce:

```glsl
shader_type spatial;
render_mode unshaded, cull_disabled;

uniform sampler2D NORMAL_TEXTURE : hint_normal_roughness_texture, filter_linear_mipmap;

void vertex(){
	VERTEX *= 2.0;
	POSITION = vec4(VERTEX, 1.0);
}

void fragment(){
	ALBEDO = texture(NORMAL_TEXTURE, SCREEN_UV).rgb;
}
```

### Minimal reproduction project

N/A
}
void RenderForwardClustered::_geometry_instance_update(RenderGeometryInstance *p_geometry_instance) {
	RendererRD::MeshStorage *mesh_storage = RendererRD::MeshStorage::get_singleton();
	RendererRD::ParticlesStorage *particles_storage = RendererRD::ParticlesStorage::get_singleton();
	GeometryInstanceForwardClustered *ginstance = static_cast<GeometryInstanceForwardClustered *>(p_geometry_instance);
	if (ginstance->data->dirty_dependencies) {
		ginstance->data->dependency_tracker.update_begin();
	}
	
	switch (ginstance->data->base_type) {
		case RS::INSTANCE_MESH: {
			const RID *materials = nullptr;
			uint32_t surface_count;
			RID mesh = ginstance->data->base;
			materials = mesh_storage->mesh_get_surface_count_and_materials(mesh, surface_count);
			if (materials) {
				
				const RID *inst_materials = ginstance->data->surface_materials.ptr();
				uint32_t surf_mat_count = ginstance->data->surface_materials.size();
				for (uint32_t j = 0; j < surface_count; j++) {
					RID material = (j < surf_mat_count && inst_materials[j].is_valid()) ? inst_materials[j] : materials[j];
					_geometry_instance_add_surface(ginstance, j, material, mesh);
				}
			}
			ginstance->instance_count = 1;
		} break;
		case RS::INSTANCE_MULTIMESH: {
			RID mesh = mesh_storage->multimesh_get_mesh(ginstance->data->base);
			if (mesh.is_valid()) {
				const RID *materials = nullptr;