### 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)

ERR_FAIL_COND(p_event.is_null());
	Ref<InputEventMouseButton> mb = p_event;
	if (mb.is_valid()) {
		if (!mb->is_pressed()) {
			gui.mouse_focus_mask.clear_flag(mouse_button_to_mask(mb->get_button_index())); 
		}
	}
}
List<Control *>::Element *Viewport::_gui_add_root_control(Control *p_control) {
	gui.roots_order_dirty = true;
	return gui.roots.push_back(p_control);
}
void Viewport::gui_set_root_order_dirty() {
	ERR_MAIN_THREAD_GUARD;
	gui.roots_order_dirty = true;
}
void Viewport::_gui_force_drag(Control *p_base, const Variant &p_data, Control *p_control) {
	ERR_FAIL_COND_MSG(p_data.get_type() == Variant::NIL, "Drag data must be a value.");
	gui.dragging = true;
	gui.drag_data = p_data;
	gui.mouse_focus = nullptr;
	if (p_control) {
		_gui_set_drag_preview(p_base, p_control);
	}
	_propagate_viewport_notification(this, NOTIFICATION_DRAG_BEGIN);
}
void Viewport::_gui_set_drag_preview(Control *p_base, Control *p_control) {