### 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)

return p_property;
	} else if (p_target == XInternAtom(x11_display, "SAVE_TARGETS", 0)) {
		
		XChangeProperty(x11_display,
				p_requestor,
				p_property,
				XInternAtom(x11_display, "NULL", False),
				32,
				PropModeReplace,
				nullptr,
				0);
		return p_property;
	} else if (p_target == XInternAtom(x11_display, "UTF8_STRING", 0) ||
			p_target == XInternAtom(x11_display, "COMPOUND_TEXT", 0) ||
			p_target == XInternAtom(x11_display, "TEXT", 0) ||
			p_target == XA_STRING ||
			p_target == XInternAtom(x11_display, "text/plain;charset=utf-8", 0) ||
			p_target == XInternAtom(x11_display, "text/plain", 0)) {
		
		
		CharString clip;
		static const char *target_type = "PRIMARY";
		if (p_selection != None && get_atom_name(x11_display, p_selection) == target_type) {
			clip = internal_clipboard_primary.utf8();
		} else {
			clip = internal_clipboard.utf8();
		}
		XChangeProperty(x11_display,
				p_requestor,
				p_property,