### Godot version

4.0.3-stable

### System information

Windows 10

### Issue description

In some projects ViewportTexture remains pink and doesn't render viewport content after upgrading from 4.0.2-stable to 4.0.3-stable. If a pair of files viewport.h/viewport.cpp are downgraded back to what they were in 4.0.2-stable, problem goes away.

This is how it looks in 4.0.3-stable:
![4 0 3_stable_viewport_4 0 3](https://github.com/godotengine/godot/assets/1449921/44c191a9-4b67-4b02-90b6-4ab615f62a73)

And this is how it looks if viewport.h/viewport.cpp are downgraded back to what they were in 4.0.2-stable.
![4 0 3_stable_viewport_4 0 2](https://github.com/godotengine/godot/assets/1449921/f5abc605-f129-4222-9c0e-e9a07621dd9d)



### Steps to reproduce

Unfortunately, I cannot come up wit a simple demo project reproducing the problem. It exists in some projects and doesn't exist in others.


### Minimal reproduction project

Cannot produce a simple project reproducing the problem. In simple projects it works fine.
#ifndef _3D_DISABLED
	if (use_xr) {
		if (XRServer::get_singleton() != nullptr) {
			Ref<XRInterface> xr_interface = XRServer::get_singleton()->get_primary_interface();
			if (xr_interface.is_valid() && xr_interface->is_initialized()) {
				Size2 xr_size = xr_interface->get_render_target_size();
				return (Size2i)xr_size;
			}
		}
		return Size2i();
	}
#endif 
	return size;
}
Size2i Viewport::_get_size_2d_override() const {