### 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
depth_pass_clear.push_back(Color(0.5, 0.5, 0.5, 0));
			} break;
			case PASS_MODE_DEPTH_NORMAL_ROUGHNESS_VOXEL_GI: {
				depth_framebuffer = rb_data->get_depth_fb(RenderBufferDataForwardClustered::DEPTH_FB_ROUGHNESS_VOXELGI);
				depth_pass_clear.push_back(Color(0.5, 0.5, 0.5, 0));
				depth_pass_clear.push_back(Color(0, 0, 0, 0));
			} break;
			default: {
			};
		}
	}
	bool using_sss = rb_data.is_valid() && !is_reflection_probe && scene_state.used_sss && ss_effects->sss_get_quality() != RS::SUB_SURFACE_SCATTERING_QUALITY_DISABLED;
	if (using_sss && !using_separate_specular) {
		using_separate_specular = true;
		color_pass_flags |= COLOR_PASS_FLAG_SEPARATE_SPECULAR;
		color_framebuffer = rb_data->get_color_pass_fb(color_pass_flags);
	}
	RID radiance_texture;
	bool draw_sky = false;
	bool draw_sky_fog_only = false;
	
	float sky_energy_multiplier = 1.0 / _render_buffers_get_luminance_multiplier();
	Color clear_color;
	bool keep_color = false;
	if (get_debug_draw_mode() == RS::VIEWPORT_DEBUG_DRAW_OVERDRAW) {
		clear_color = Color(0, 0, 0, 1); 
	} else if (is_environment(p_render_data->environment)) {
		RS::EnvironmentBG bg_mode = environment_get_background(p_render_data->environment);
		float bg_energy_multiplier = environment_get_bg_energy_multiplier(p_render_data->environment);
		bg_energy_multiplier *= environment_get_bg_intensity(p_render_data->environment);