### 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)

if (gui.sub_windows.size() < 2) {
		return;
	}
	if (!gui.sub_windows[gui.sub_windows.size() - 1].window->get_flag(Window::FLAG_ALWAYS_ON_TOP)) {
		int index = gui.sub_windows.size() - 1;
		while (index > 0 && gui.sub_windows[index - 1].window->get_flag(Window::FLAG_ALWAYS_ON_TOP)) {
			--index;
		}
		if (index != (gui.sub_windows.size() - 1)) {
			SubWindow sw = gui.sub_windows[gui.sub_windows.size() - 1];
			gui.sub_windows.remove_at(gui.sub_windows.size() - 1);
			gui.sub_windows.insert(index, sw);
		}
	}
	for (int i = 0; i < gui.sub_windows.size(); i++) {
		RS::get_singleton()->canvas_item_set_draw_index(gui.sub_windows[i].canvas_item, i);
	}
}
void Viewport::_sub_window_register(Window *p_window) {