### 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
uint32_t surface_count;
				materials = mesh_storage->mesh_get_surface_count_and_materials(mesh, surface_count);
				if (materials) {
					for (uint32_t j = 0; j < surface_count; j++) {
						_geometry_instance_add_surface(ginstance, j, materials[j], mesh);
					}
				}
				ginstance->instance_count = mesh_storage->multimesh_get_instances_to_draw(ginstance->data->base);
			}
		} break;
#if 0
		case RS::INSTANCE_IMMEDIATE: {
			RasterizerStorageGLES3::Immediate *immediate = storage->immediate_owner.get_or_null(inst->base);
			ERR_CONTINUE(!immediate);
			_add_geometry(immediate, inst, nullptr, -1, p_depth_pass, p_shadow_pass);
		} break;
#endif
		case RS::INSTANCE_PARTICLES: {
			int draw_passes = particles_storage->particles_get_draw_passes(ginstance->data->base);
			for (int j = 0; j < draw_passes; j++) {
				RID mesh = particles_storage->particles_get_draw_pass_mesh(ginstance->data->base, j);
				if (!mesh.is_valid()) {
					continue;
				}
				const RID *materials = nullptr;
				uint32_t surface_count;
				materials = mesh_storage->mesh_get_surface_count_and_materials(mesh, surface_count);
				if (materials) {
					for (uint32_t k = 0; k < surface_count; k++) {
						_geometry_instance_add_surface(ginstance, k, materials[k], mesh);