### 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)

Rect2 swrect = Rect2i(sw->get_position(), sw->get_size());
					if (!sw->get_flag(Window::FLAG_BORDERLESS)) {
						int title_height = sw->get_theme_constant(SNAME("title_height"));
						swrect.position.y -= title_height;
						swrect.size.y += title_height;
					}
					if (swrect.has_point(viewport_pos)) {
						viewport_under = sw;
						viewport_pos -= sw->get_position();
					}
				}
				if (!viewport_under) {
					
					viewport_under = embedder;
				}
			} else {
				
				Vector2i screen_mouse_pos = DisplayServer::get_singleton()->mouse_get_position();
				DisplayServer::WindowID window_id = DisplayServer::get_singleton()->get_window_at_screen_position(screen_mouse_pos);
				if (window_id != DisplayServer::INVALID_WINDOW_ID) {
					ObjectID object_under = DisplayServer::get_singleton()->window_get_attached_instance_id(window_id);
					if (object_under != ObjectID()) { 
						Window *w = Object::cast_to<Window>(ObjectDB::get_instance(object_under));
						if (w) {
							viewport_under = w;
							viewport_pos = screen_mouse_pos - w->get_position();
						}
					}
				}
			}