### 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)

void set_size_2d_override(const Size2i &p_size);
	Size2i get_size_2d_override() const;
	void set_size_2d_override_stretch(bool p_enable);
	bool is_size_2d_override_stretch_enabled() const override;
	void set_update_mode(UpdateMode p_mode);
	UpdateMode get_update_mode() const;
	void set_clear_mode(ClearMode p_mode);
	ClearMode get_clear_mode() const;
	virtual Transform2D get_screen_transform_internal(bool p_absolute_position = false) const override;
	virtual Transform2D get_popup_base_transform() const override;
	void _validate_property(PropertyInfo &p_property) const;
	SubViewport();
	~SubViewport();
};
VARIANT_ENUM_CAST(Viewport::Scaling3DMode);
VARIANT_ENUM_CAST(SubViewport::UpdateMode);
VARIANT_ENUM_CAST(Viewport::PositionalShadowAtlasQuadrantSubdiv);
VARIANT_ENUM_CAST(Viewport::MSAA);
VARIANT_ENUM_CAST(Viewport::ScreenSpaceAA);
VARIANT_ENUM_CAST(Viewport::DebugDraw);
VARIANT_ENUM_CAST(Viewport::SDFScale);
VARIANT_ENUM_CAST(Viewport::SDFOversize);
VARIANT_ENUM_CAST(Viewport::VRSMode);
VARIANT_ENUM_CAST(SubViewport::ClearMode);
VARIANT_ENUM_CAST(Viewport::RenderInfo);
VARIANT_ENUM_CAST(Viewport::RenderInfoType);
VARIANT_ENUM_CAST(Viewport::DefaultCanvasItemTextureFilter);
VARIANT_ENUM_CAST(Viewport::DefaultCanvasItemTextureRepeat);
#endif