### Godot version

4.1.dev 2e273f0e35800f2bcc7c05db54100caa97928f69

### System information

macOS 13.4

### Issue description

Removing a SpinBox from the node tree using `remove_child` during the line edit text submit signal will crash the engine.

```
handle_crash: Program crashed with signal 11
Engine version: Godot Engine v4.1.dev.custom_build (2e273f0e35800f2bcc7c05db54100caa97928f69)
Dumping the backtrace. Please include this when reporting the bug to the project developer.
[1] 1   libsystem_platform.dylib            0x0000000183b5aa24 _sigtramp + 56
[2] Viewport::gui_get_focus_owner() (in godot.macos.editor.arm64) + 32
[3] SpinBox::_line_edit_focus_exit() (in godot.macos.editor.arm64) + 28
[4] CallQueue::_call_function(Callable const&, Variant const*, int, bool) (in godot.macos.editor.arm64) + 336
[5] CallQueue::flush() (in godot.macos.editor.arm64) + 908
[6] SceneTree::physics_process(double) (in godot.macos.editor.arm64) + 244
[7] Main::iteration() (in godot.macos.editor.arm64) + 528
```

### Steps to reproduce

Open the minimal reproduction project, click on the SpinBox, press enter, and the engine crashes.

### Minimal reproduction project

[SpinBoxTextSubmitCrash.zip](https://github.com/godotengine/godot/files/11631081/SpinBoxTextSubmitCrash.zip)

title_text.draw(sw.canvas_item, r.position + Point2(x, y), title_color);
		bool pressed = gui.subwindow_focused == sw.window && gui.subwindow_drag == SUB_WINDOW_DRAG_CLOSE && gui.subwindow_drag_close_inside;
		Ref<Texture2D> close_icon = p_window->get_theme_icon(pressed ? "close_pressed" : "close");
		close_icon->draw(sw.canvas_item, r.position + Vector2(r.size.width - close_h_ofs, -close_v_ofs));
	}
	RS::get_singleton()->canvas_item_add_texture_rect(sw.canvas_item, r, sw.window->get_texture()->get_rid());
}
void Viewport::_sub_window_grab_focus(Window *p_window) {
	if (p_window == nullptr) {
		
		if (gui.subwindow_focused) {
			gui.subwindow_focused->_event_callback(DisplayServer::WINDOW_EVENT_FOCUS_OUT);
			gui.subwindow_focused = nullptr;
			gui.subwindow_drag = SUB_WINDOW_DRAG_DISABLED;
		}
		Window *this_window = Object::cast_to<Window>(this);
		if (this_window) {
			this_window->_event_callback(DisplayServer::WINDOW_EVENT_FOCUS_IN);
		}
		return;
	}
	int index = _sub_window_find(p_window);
	ERR_FAIL_COND(index == -1);
	if (p_window->get_flag(Window::FLAG_NO_FOCUS)) {
		
		SubWindow sw = gui.sub_windows[index];
		gui.sub_windows.remove_at(index);
		gui.sub_windows.push_back(sw);
		index = gui.sub_windows.size() - 1;
		_sub_window_update_order();