### 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;
	if (gui.subwindow_focused) {
		gui.subwindow_focused->push_text_input(p_text);
		return;
	}
	if (gui.key_focus) {
		gui.key_focus->call("set_text", p_text);
	}
}
Viewport::SubWindowResize Viewport::_sub_window_get_resize_margin(Window *p_subwindow, const Point2 &p_point) {
	if (p_subwindow->get_flag(Window::FLAG_BORDERLESS) || p_subwindow->get_flag(Window::FLAG_RESIZE_DISABLED)) {
		return SUB_WINDOW_RESIZE_DISABLED;
	}
	Rect2i r = Rect2i(p_subwindow->get_position(), p_subwindow->get_size());
	int title_height = p_subwindow->get_theme_constant(SNAME("title_height"));
	r.position.y -= title_height;
	r.size.y += title_height;
	if (r.has_point(p_point)) {
		return SUB_WINDOW_RESIZE_DISABLED; 
	}
	int dist_x = p_point.x < r.position.x ? (p_point.x - r.position.x) : (p_point.x > (r.position.x + r.size.x) ? (p_point.x - (r.position.x + r.size.x)) : 0);
	int dist_y = p_point.y < r.position.y ? (p_point.y - r.position.y) : (p_point.y > (r.position.y + r.size.y) ? (p_point.y - (r.position.y + r.size.y)) : 0);
	int limit = p_subwindow->get_theme_constant(SNAME("resize_margin"));
	if (ABS(dist_x) > limit) {
		return SUB_WINDOW_RESIZE_DISABLED;
	}