### 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)

GDCLASS(SubViewport, Viewport);
public:
	enum ClearMode {
		CLEAR_MODE_ALWAYS,
		CLEAR_MODE_NEVER,
		CLEAR_MODE_ONCE
	};
	enum UpdateMode {
		UPDATE_DISABLED,
		UPDATE_ONCE, 
		UPDATE_WHEN_VISIBLE, 
		UPDATE_WHEN_PARENT_VISIBLE,
		UPDATE_ALWAYS
	};
private:
	UpdateMode update_mode = UPDATE_WHEN_VISIBLE;
	ClearMode clear_mode = CLEAR_MODE_ALWAYS;
	bool size_2d_override_stretch = false;
	void _internal_set_size(const Size2i &p_size, bool p_force = false);
protected:
	static void _bind_methods();
	virtual DisplayServer::WindowID get_window_id() const override;
	void _notification(int p_what);
public:
	void set_size(const Size2i &p_size);
	Size2i get_size() const;
	void set_size_force(const Size2i &p_size);