### 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.
gui.subwindow_drag_close_rect = close_rect;
					} else {
						gui.subwindow_drag = SUB_WINDOW_DRAG_MOVE;
					}
					gui.subwindow_drag_from = mb->get_position();
					gui.subwindow_drag_pos = sw.window->get_position();
					_sub_window_update(sw.window);
				} else {
					gui.subwindow_resize_mode = _sub_window_get_resize_margin(sw.window, mb->get_position());
					if (gui.subwindow_resize_mode != SUB_WINDOW_RESIZE_DISABLED) {
						if (gui.subwindow_focused != sw.window) {
							
							_sub_window_grab_focus(sw.window);
						}
						gui.subwindow_resize_from_rect = r;
						gui.subwindow_drag_from = mb->get_position();
						gui.subwindow_drag = SUB_WINDOW_DRAG_RESIZE;
						click_on_window = sw.window;
					}
				}
			}
			if (!click_on_window && r.has_point(mb->get_position())) {
				
				if (gui.subwindow_focused != sw.window) {
					
					_sub_window_grab_focus(sw.window);
				}
				click_on_window = sw.window;
			}
			if (click_on_window) {