### 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 (!gui.tooltip_control) {
		return;
	}
	
	Control *tooltip_owner = nullptr;
	String tooltip_text = _gui_get_tooltip(
			gui.tooltip_control,
			gui.tooltip_control->get_global_transform().xform_inv(gui.last_mouse_pos),
			&tooltip_owner);
	tooltip_text = tooltip_text.strip_edges();
	if (tooltip_text.is_empty()) {
		return; 
	}
	
	if (gui.tooltip_popup) {
		memdelete(gui.tooltip_popup);
	}
	if (!tooltip_owner) {
		return;
	}
	
	PopupPanel *panel = memnew(PopupPanel);