### Godot version

v4.0 rc6

### System information

Windows 10

### Issue description

When using a ViewportTexture from a SubViewport on a TextureRect, it throws errors after running the scene once and then switching scenes in the editor.
![Pasted image 20230227212626](https://user-images.githubusercontent.com/44676282/221680047-984fa03e-33d1-4856-9a7f-1700b28423cf.png)


### Steps to reproduce

Run the canvas-scene once.
Switch to another scene in the editor.
Switch back to the canvas-scene

### Minimal reproduction project

[ViewportTextureError.zip](https://github.com/godotengine/godot/files/10844099/ViewportTextureError.zip)

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;
	virtual bool is_directly_attached_to_screen() const override;
	virtual bool is_attached_in_viewport() const override;
	virtual bool is_sub_viewport() const override { return true; };
	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