### 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)

if (co && co->is_inside_tree()) {
				if (p_clean_all_frames && p_paused_only && co->can_process()) {
					continue;
				}
				co->_mouse_shape_exit(E.key.second);
			}
		}
		shapes_to_erase.push_back(E.key);
	}
	while (shapes_to_erase.size()) {
		physics_2d_shape_mouseover.erase(shapes_to_erase.front()->get());
		shapes_to_erase.pop_front();
	}
}
void Viewport::_gui_grab_click_focus(Control *p_control) {
	gui.mouse_click_grabber = p_control;
	call_deferred(SNAME("_post_gui_grab_click_focus"));
}
void Viewport::_post_gui_grab_click_focus() {
	Control *focus_grabber = gui.mouse_click_grabber;
	if (!focus_grabber) {
		
		return;
	}
	gui.mouse_click_grabber = nullptr;
	if (gui.mouse_focus) {
		if (gui.mouse_focus == focus_grabber) {
			return;
		}
		BitField<MouseButtonMask> mask = gui.mouse_focus_mask;