### 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.
ERR_MAIN_THREAD_GUARD;
	_internal_set_size(p_size);
}
void SubViewport::set_size_force(const Size2i &p_size) {
	ERR_MAIN_THREAD_GUARD;
	// Use only for setting the size from the parent SubViewportContainer with enabled stretch mode.
	// Don't expose function to scripting.
	_internal_set_size(p_size, true);
}
void SubViewport::_internal_set_size(const Size2i &p_size, bool p_force) {
	SubViewportContainer *c = Object::cast_to<SubViewportContainer>(get_parent());
	if (!p_force && c && c->is_stretch_enabled()) {
#ifdef DEBUG_ENABLED
		WARN_PRINT("Can't change the size of a `SubViewport` with a `SubViewportContainer` parent that has `stretch` enabled. Set `SubViewportContainer.stretch` to `false` to allow changing the size manually.");
#endif // DEBUG_ENABLED
		return;
	}
	_set_size(p_size, _get_size_2d_override(), true);
	if (c) {
		c->update_minimum_size();
	}
}
Size2i SubViewport::get_size() const {