### 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)

max_size.x = MAX(max_size.x, 1);
					max_size.y = MAX(max_size.y, 1);
					if (r.size.x > max_size.x) {
						r.size.x = max_size.x;
					}
					if (r.size.y > max_size.y) {
						r.size.y = max_size.y;
					}
				}
				gui.subwindow_focused->_rect_changed_callback(r);
			}
			if (gui.subwindow_focused) { 
				_sub_window_update(gui.subwindow_focused);
			}
		}
		return true; 
	}
	Ref<InputEventMouseButton> mb = p_event;
	
	if (mb.is_valid() && mb->is_pressed() && mb->get_button_index() == MouseButton::LEFT) {
		bool click_on_window = false;
		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;