### 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 shadow_pass_index = scene_state.shadow_passes.size();
	SceneState::ShadowPass shadow_pass;
	RenderSceneDataRD scene_data;
	scene_data.cam_projection = p_projection;
	scene_data.cam_transform = p_transform;
	scene_data.view_projection[0] = p_projection;
	scene_data.z_far = p_zfar;
	scene_data.z_near = 0.0;
	scene_data.lod_distance_multiplier = p_lod_distance_multiplier;
	scene_data.dual_paraboloid_side = p_use_dp_flip ? -1 : 1;
	scene_data.opaque_prepass_threshold = 0.1f;
	scene_data.time = time;
	scene_data.time_step = time_step;
	RenderDataRD render_data;
	render_data.scene_data = &scene_data;
	render_data.cluster_size = 1;
	render_data.cluster_max_elements = 32;
	render_data.instances = &p_instances;
	render_data.render_info = p_render_info;
	_setup_environment(&render_data, true, Vector2(1, 1), !p_flip_y, Color(), false, p_use_pancake, shadow_pass_index);
	if (get_debug_draw_mode() == RS::VIEWPORT_DEBUG_DRAW_DISABLE_LOD) {
		scene_data.screen_mesh_lod_threshold = 0.0;
	} else {
		scene_data.screen_mesh_lod_threshold = p_screen_mesh_lod_threshold;
	}
	PassMode pass_mode = p_use_dp ? PASS_MODE_SHADOW_DP : PASS_MODE_SHADOW;