### 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
RendererRD::LightStorage *light_storage = RendererRD::LightStorage::get_singleton();
	ERR_FAIL_COND(!light_storage->owns_light_instance(p_light));
	RID base = light_storage->light_instance_get_base_light(p_light);
	Rect2i atlas_rect;
	uint32_t atlas_size = 1;
	RID atlas_fb;
	bool reverse_cull_face = light_storage->light_get_reverse_cull_face_mode(base);
	bool using_dual_paraboloid = false;
	bool using_dual_paraboloid_flip = false;
	Vector2i dual_paraboloid_offset;
	RID render_fb;
	RID render_texture;
	float zfar;
	bool use_pancake = false;
	bool render_cubemap = false;
	bool finalize_cubemap = false;
	bool flip_y = false;
	Projection light_projection;
	Transform3D light_transform;
	if (light_storage->light_get_type(base) == RS::LIGHT_DIRECTIONAL) {