### 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)

int index = _sub_window_find(p_window);
	ERR_FAIL_COND(index == -1);
	ERR_FAIL_NULL(RenderingServer::get_singleton());
	RS::get_singleton()->free(gui.sub_windows[index].canvas_item);
	gui.sub_windows.remove_at(index);
	if (gui.sub_windows.size() == 0) {
		RS::get_singleton()->free(subwindow_canvas);
		subwindow_canvas = RID();
	}
	if (gui.subwindow_focused == p_window) {
		Window *new_focused_window;
		Window *parent_visible = p_window->get_parent_visible_window();
		gui.subwindow_drag = SUB_WINDOW_DRAG_DISABLED;
		gui.subwindow_focused->_event_callback(DisplayServer::WINDOW_EVENT_FOCUS_OUT);
		if (parent_visible) {
			new_focused_window = parent_visible;
		} else {
			new_focused_window = Object::cast_to<Window>(this);
		}
		if (new_focused_window) {
			int new_focused_index = _sub_window_find(new_focused_window);
			if (new_focused_index != -1) {
				gui.subwindow_focused = new_focused_window;
			} else {
				gui.subwindow_focused = nullptr;
			}
			new_focused_window->_event_callback(DisplayServer::WINDOW_EVENT_FOCUS_IN);