### Godot version

v4.0 rc6

### System information

Windows 10

### Issue description

When using a ViewportTexture from a SubViewport on a TextureRect, it throws errors after running the scene once and then switching scenes in the editor.
![Pasted image 20230227212626](https://user-images.githubusercontent.com/44676282/221680047-984fa03e-33d1-4856-9a7f-1700b28423cf.png)


### Steps to reproduce

Run the canvas-scene once.
Switch to another scene in the editor.
Switch back to the canvas-scene

### Minimal reproduction project

[ViewportTextureError.zip](https://github.com/godotengine/godot/files/10844099/ViewportTextureError.zip)

for (Camera3D *E : camera_3d_set) {
					if (first == nullptr || first->is_greater_than(E)) {
						first = E;
					}
				}
				if (first) {
					first->make_current();
				}
			}
#endif 
		} break;
		case NOTIFICATION_EXIT_TREE: {
			_gui_cancel_tooltip();
			RenderingServer::get_singleton()->viewport_set_scenario(viewport, RID());
			RenderingServer::get_singleton()->viewport_remove_canvas(viewport, current_canvas);
			if (contact_2d_debug.is_valid()) {
				RenderingServer::get_singleton()->free(contact_2d_debug);
				contact_2d_debug = RID();
			}
			if (contact_3d_debug_multimesh.is_valid()) {
				RenderingServer::get_singleton()->free(contact_3d_debug_multimesh);
				RenderingServer::get_singleton()->free(contact_3d_debug_instance);
				contact_3d_debug_instance = RID();
				contact_3d_debug_multimesh = RID();
			}
			remove_from_group("_viewports");
			set_physics_process_internal(false);
			RS::get_singleton()->viewport_set_active(viewport, false);
			RenderingServer::get_singleton()->viewport_set_parent_viewport(viewport, RID());
		} break;