### 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
Ref<RenderSceneBuffersRD> rb;
	if (p_render_data && p_render_data->render_buffers.is_valid()) {
		rb = p_render_data->render_buffers;
	}
	if (rb.is_valid() && rb->has_custom_data(RB_SCOPE_SDFGI)) {
		Ref<RendererRD::GI::SDFGI> sdfgi = rb->get_custom_data(RB_SCOPE_SDFGI);
		float exposure_normalization = 1.0;
		if (p_render_data->camera_attributes.is_valid()) {
			exposure_normalization = RSG::camera_attributes->camera_attributes_get_exposure_normalization_factor(p_render_data->camera_attributes);
		}
		for (int i = 0; i < p_render_data->render_sdfgi_region_count; i++) {
			sdfgi->render_region(rb, p_render_data->render_sdfgi_regions[i].region, p_render_data->render_sdfgi_regions[i].instances, exposure_normalization);
		}
		if (p_render_data->sdfgi_update_data->update_static) {
			sdfgi->render_static_lights(p_render_data, rb, p_render_data->sdfgi_update_data->static_cascade_count, p_render_data->sdfgi_update_data->static_cascade_indices, p_render_data->sdfgi_update_data->static_positional_lights);
		}
	}
}
void RenderForwardClustered::_debug_draw_cluster(Ref<RenderSceneBuffersRD> p_render_buffers) {