### 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 (p_control) {
		gui.drag_successful = _gui_drop(p_control, p_pos, false);
	} else {
		gui.drag_successful = false;
	}
	Control *drag_preview = _gui_get_drag_preview();
	if (drag_preview) {
		memdelete(drag_preview);
		gui.drag_preview_id = ObjectID();
	}
	gui.drag_data = Variant();
	gui.dragging = false;
	gui.drag_mouse_over = nullptr;
	_propagate_viewport_notification(this, NOTIFICATION_DRAG_END);
	
	update_mouse_cursor_state();
}
void Viewport::_gui_cleanup_internal_state(Ref<InputEvent> p_event) {