### 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)

}
			}
			[[fallthrough]];
		}
		case WM_CHAR: {
			ERR_BREAK(key_event_pos >= KEY_EVENT_BUFFER_SIZE);
			
			KeyEvent ke;
			ke.shift = (wParam != VK_SHIFT) ? shift_mem : false;
			ke.alt = (!(wParam == VK_MENU && (uMsg == WM_KEYDOWN || uMsg == WM_SYSKEYDOWN))) ? alt_mem : false;
			ke.control = (wParam != VK_CONTROL) ? control_mem : false;
			ke.meta = meta_mem;
			ke.uMsg = uMsg;
			ke.window_id = window_id;
			if (ke.uMsg == WM_SYSKEYDOWN) {
				ke.uMsg = WM_KEYDOWN;
			}
			if (ke.uMsg == WM_SYSKEYUP) {
				ke.uMsg = WM_KEYUP;
			}
			ke.wParam = wParam;
			ke.lParam = lParam;
			key_event_buffer[key_event_pos++] = ke;
		} break;
		case WM_IME_COMPOSITION: {
			CANDIDATEFORM cf;
			cf.dwIndex = 0;
			cf.dwStyle = CFS_CANDIDATEPOS;
			cf.ptCurrentPos.x = windows[window_id].im_position.x;
			cf.ptCurrentPos.y = windows[window_id].im_position.y;