### 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)

0, LONG_MAX, 
							True, 
							AnyPropertyType, 
							&type, 
							&format, 
							&len, &bytes_left, 
							&data);
					DEBUG_LOG_X11("PropertyNotify: len=%lu, format=%i\n", len, format);
					if (result == Success) {
						if (data && (len > 0)) {
							uint32_t prev_size = incr_data.size();
							if (prev_size == 0) {
								
								unsigned long initial_size = *(unsigned long *)data;
								incr_data.resize(initial_size);
							} else {
								
								incr_data.resize(MAX(data_size + len, prev_size));
								memcpy(incr_data.ptr() + data_size, data, len);
								data_size += len;
							}
						} else {
							
							done = true;
							success = true;
						}
					} else {
						print_verbose("Failed to get selection data chunk.");
						done = true;
					}