### Godot version

Godot Engine v4.0.stable.official.92bee43ad

### System information

Windows 10

### Issue description

The documentation states that passing ```null``` into the image parameter of ```set_custom_mouse_cursor``` will change it back to the system cursor, however I find that it removes the cursor's image entirely, rather than setting it to the system's cursor.


### Steps to reproduce

```var isimage = false
var theimage = load("res://final.png")

func _on_my_button_pressed():
    if isimage == false:
        Input.set_custom_mouse_cursor(theimage, Input.CURSOR_ARROW, Vector2(16,16))
        isimage = true
        
    else:
        Input.set_custom_mouse_cursor(null)
        isimage = false```

When the button is pressed, the cursor is meant to change to the new cursor. When it has been pressed a second time, it changes back to the default cursor. However, upon pressing it a second time, it simply disappears. The cursor becomes visible again when the cursor exits and re-enters the window.

### Minimal reproduction project

[null mouse.zip](https://github.com/godotengine/godot/files/10901969/null.mouse.zip)

wintab_WTClose(windows[MAIN_WINDOW_ID].wtctx);
			windows[MAIN_WINDOW_ID].wtctx = 0;
		}
		DestroyWindow(windows[MAIN_WINDOW_ID].hWnd);
	}
#if defined(VULKAN_ENABLED)
	if (rendering_device_vulkan) {
		rendering_device_vulkan->finalize();
		memdelete(rendering_device_vulkan);
		rendering_device_vulkan = nullptr;
	}
	if (context_vulkan) {
		memdelete(context_vulkan);
		context_vulkan = nullptr;
	}
#endif
	if (restore_mouse_trails > 1) {
		SystemParametersInfoA(SPI_SETMOUSETRAILS, restore_mouse_trails, 0, 0);
	}
#ifdef GLES3_ENABLED
	if (gl_manager) {
		memdelete(gl_manager);
		gl_manager = nullptr;
	}
#endif
	if (tts) {
		memdelete(tts);
	}
}