### 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)

camera_3d_set.insert(p_camera);
	return camera_3d_set.size() == 1;
}
void Viewport::_camera_3d_remove(Camera3D *p_camera) {
	camera_3d_set.erase(p_camera);
	if (camera_3d == p_camera) {
		camera_3d->notification(Camera3D::NOTIFICATION_LOST_CURRENT);
		camera_3d = nullptr;
	}
}
void Viewport::_camera_3d_make_next_current(Camera3D *p_exclude) {
	for (Camera3D *E : camera_3d_set) {
		if (p_exclude == E) {
			continue;
		}
		if (!E->is_inside_tree()) {
			continue;
		}
		if (camera_3d != nullptr) {
			return;
		}
		E->make_current();
	}
}
void Viewport::enable_camera_3d_override(bool p_enable) {