### 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)

XCloseDisplay(x11_display);
			return;
		}
	}
	char *modifiers = nullptr;
	Bool xkb_dar = False;
	XAutoRepeatOn(x11_display);
	xkb_dar = XkbSetDetectableAutoRepeat(x11_display, True, nullptr);
	
	if (xkb_dar == True) {
#ifdef X_HAVE_UTF8_STRING
		
		
		modifiers = XSetLocaleModifiers("");
#endif
	}
	if (modifiers == nullptr) {
		if (OS::get_singleton()->is_stdout_verbose()) {
			WARN_PRINT("IME is disabled");
		}
		XSetLocaleModifiers("@im=none");
		WARN_PRINT("Error setting locale modifiers");
	}
	const char *err;
	int xrandr_major = 0;
	int xrandr_minor = 0;
	int event_base, error_base;
	xrandr_ext_ok = XRRQueryExtension(x11_display, &event_base, &error_base);
	xrandr_handle = dlopen("libXrandr.so.2", RTLD_LAZY);
	if (!xrandr_handle) {