### 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.
}
	Ref<InputEventMouseButton> mb = p_event;
	
	if (mb.is_valid() && mb->is_pressed() && mb->get_button_index() == MouseButton::LEFT) {
		Window *click_on_window = nullptr;
		for (int i = gui.sub_windows.size() - 1; i >= 0; i--) {
			SubWindow sw = gui.sub_windows.write[i];
			
			Rect2i r = Rect2i(sw.window->get_position(), sw.window->get_size());
			if (!sw.window->get_flag(Window::FLAG_BORDERLESS)) {
				
				int title_height = sw.window->get_theme_constant(SNAME("title_height"));
				Rect2i title_bar = r;
				title_bar.position.y -= title_height;
				title_bar.size.y = title_height;
				if (title_bar.size.y > 0 && title_bar.has_point(mb->get_position())) {
					click_on_window = sw.window;
					int close_h_ofs = sw.window->get_theme_constant(SNAME("close_h_offset"));
					int close_v_ofs = sw.window->get_theme_constant(SNAME("close_v_offset"));
					Ref<Texture2D> close_icon = sw.window->get_theme_icon(SNAME("close"));
					Rect2 close_rect;
					close_rect.position = Vector2(r.position.x + r.size.x - close_h_ofs, r.position.y - close_v_ofs);
					close_rect.size = close_icon->get_size();
					if (gui.subwindow_focused != sw.window) {
						
						_sub_window_grab_focus(sw.window);
					}
					if (close_rect.has_point(mb->get_position())) {
						gui.subwindow_drag = SUB_WINDOW_DRAG_CLOSE;
						gui.subwindow_drag_close_inside = true;