### 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)

bool stopped = false;
			if (gui.mouse_focus && gui.mouse_focus->can_process()) {
				stopped = _gui_call_input(gui.mouse_focus, mb);
			}
			if (stopped) {
				set_input_as_handled();
			}
			if (gui.dragging && mb->get_button_index() == MouseButton::LEFT) {
				
				_perform_drop(gui.mouse_focus, pos);
			}
			_gui_cancel_tooltip();
		} else {
			if (gui.dragging && mb->get_button_index() == MouseButton::LEFT) {
				_perform_drop(gui.drag_mouse_over, gui.drag_mouse_over_pos);
			}
			gui.mouse_focus_mask.clear_flag(mouse_button_to_mask(mb->get_button_index())); 
			if (!gui.mouse_focus) {
				
				return;
			}
			mb = mb->xformed_by(Transform2D()); 
			Point2 pos = gui.mouse_focus->get_global_transform_with_canvas().affine_inverse().xform(mpos);
			mb->set_position(pos);
			Control *mouse_focus = gui.mouse_focus;
			
			
			
			if (gui.mouse_focus_mask.is_empty()) {
				gui.mouse_focus = nullptr;