### 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.
if (gui.dragging) {
			
			Control *drag_preview = _gui_get_drag_preview();
			if (drag_preview) {
				drag_preview->set_position(mpos);
			}
			gui.drag_mouse_over = over;
			gui.drag_mouse_over_pos = Vector2();
			
			
			Viewport *embedder = nullptr;
			Vector2 viewport_pos;
			if (is_embedding_subwindows()) {
				embedder = this;
				viewport_pos = mpos;
			} else {
				
				Window *w = Object::cast_to<Window>(this);
				if (w) {
					if (w->is_embedded()) {
						embedder = w->get_embedder();
						viewport_pos = get_final_transform().xform(mpos) + w->get_position(); 
					}
				}
			}
			Viewport *viewport_under = nullptr;
			if (embedder) {
				
				for (int i = embedder->gui.sub_windows.size() - 1; i >= 0; i--) {
					Window *sw = embedder->gui.sub_windows[i].window;