### 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)

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	}
	
	
	
	
	
	
	
	
	
	
	
	
	
	
	
	
	KeySym keysym_keycode = 0; 
	KeySym keysym_unicode = 0; 
	
	char str[256] = {};
	XKeyEvent xkeyevent_no_mod = *xkeyevent;
	xkeyevent_no_mod.state &= ~ShiftMask;
	xkeyevent_no_mod.state &= ~ControlMask;
	XLookupString(xkeyevent, str, 255, &keysym_unicode, nullptr);
	XLookupString(&xkeyevent_no_mod, nullptr, 0, &keysym_keycode, nullptr);
	String keysym;
#ifdef XKB_ENABLED
	if (xkb_loaded_v08p) {