### 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)

ERR_MAIN_THREAD_GUARD;
	if (camera_3d_override) {
		if (camera_3d_override.size == p_size && camera_3d_override.z_near == p_z_near &&
				camera_3d_override.z_far == p_z_far && camera_3d_override.projection == Camera3DOverrideData::PROJECTION_ORTHOGONAL) {
			return;
		}
		camera_3d_override.size = p_size;
		camera_3d_override.z_near = p_z_near;
		camera_3d_override.z_far = p_z_far;
		camera_3d_override.projection = Camera3DOverrideData::PROJECTION_ORTHOGONAL;
		RenderingServer::get_singleton()->camera_set_orthogonal(camera_3d_override.rid, camera_3d_override.size, camera_3d_override.z_near, camera_3d_override.z_far);
	}
}
void Viewport::set_disable_3d(bool p_disable) {
	ERR_MAIN_THREAD_GUARD;
	disable_3d = p_disable;
	RenderingServer::get_singleton()->viewport_set_disable_3d(viewport, disable_3d);
}
bool Viewport::is_3d_disabled() const {
	ERR_READ_THREAD_GUARD_V(false);
	return disable_3d;
}
bool Viewport::is_camera_3d_override_enabled() const {
	ERR_READ_THREAD_GUARD_V(false);
	return camera_3d_override;
}
void Viewport::set_camera_3d_override_transform(const Transform3D &p_transform) {