### 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
}
		RenderListParameters render_list_params(render_list[RENDER_LIST_OPAQUE].elements.ptr(), render_list[RENDER_LIST_OPAQUE].element_info.ptr(), render_list[RENDER_LIST_OPAQUE].elements.size(), reverse_cull, PASS_MODE_COLOR, color_pass_flags, rb_data.is_null(), p_render_data->directional_light_soft_shadows, rp_uniform_set, get_debug_draw_mode() == RS::VIEWPORT_DEBUG_DRAW_WIREFRAME, Vector2(), p_render_data->scene_data->lod_distance_multiplier, p_render_data->scene_data->screen_mesh_lod_threshold, p_render_data->scene_data->view_count);
		_render_list_with_threads(&render_list_params, color_framebuffer, keep_color ? RD::INITIAL_ACTION_KEEP : RD::INITIAL_ACTION_CLEAR, will_continue_color ? RD::FINAL_ACTION_CONTINUE : RD::FINAL_ACTION_READ, depth_pre_pass ? (continue_depth ? RD::INITIAL_ACTION_CONTINUE : RD::INITIAL_ACTION_KEEP) : RD::INITIAL_ACTION_CLEAR, will_continue_depth ? RD::FINAL_ACTION_CONTINUE : RD::FINAL_ACTION_READ, c, 1.0, 0);
		if (will_continue_color && using_separate_specular) {
			
			RD::get_singleton()->draw_list_begin(rb_data->get_specular_only_fb(), RD::INITIAL_ACTION_CONTINUE, RD::FINAL_ACTION_READ, RD::INITIAL_ACTION_CONTINUE, RD::FINAL_ACTION_CONTINUE);
			RD::get_singleton()->draw_list_end();
		}
	}
	RD::get_singleton()->draw_command_end_label();
	if (debug_voxelgis) {
		
		bool will_continue_color = (can_continue_color || draw_sky || draw_sky_fog_only);
		bool will_continue_depth = (can_continue_depth || draw_sky || draw_sky_fog_only);
		Projection dc;
		dc.set_depth_correction(true);
		Projection cm = (dc * p_render_data->scene_data->cam_projection) * Projection(p_render_data->scene_data->cam_transform.affine_inverse());
		RD::DrawListID draw_list = RD::get_singleton()->draw_list_begin(color_only_framebuffer, RD::INITIAL_ACTION_CONTINUE, will_continue_color ? RD::FINAL_ACTION_CONTINUE : RD::FINAL_ACTION_READ, RD::INITIAL_ACTION_CONTINUE, will_continue_depth ? RD::FINAL_ACTION_CONTINUE : RD::FINAL_ACTION_READ);
		RD::get_singleton()->draw_command_begin_label("Debug VoxelGIs");
		for (int i = 0; i < (int)p_render_data->voxel_gi_instances->size(); i++) {
			gi.debug_voxel_gi((*p_render_data->voxel_gi_instances)[i], draw_list, color_only_framebuffer, cm, get_debug_draw_mode() == RS::VIEWPORT_DEBUG_DRAW_VOXEL_GI_LIGHTING, get_debug_draw_mode() == RS::VIEWPORT_DEBUG_DRAW_VOXEL_GI_EMISSION, 1.0);
		}
		RD::get_singleton()->draw_command_end_label();
		RD::get_singleton()->draw_list_end();
	}
	if (debug_sdfgi_probes) {
		
		bool will_continue_color = (can_continue_color || draw_sky || draw_sky_fog_only);
		bool will_continue_depth = (can_continue_depth || draw_sky || draw_sky_fog_only);
		Projection dc;