### 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)

_THREAD_SAFE_METHOD_
	p_screen = _get_screen_index(p_screen);
	EnumSizeData data = { 0, p_screen, Size2() };
	EnumDisplayMonitors(nullptr, nullptr, _MonitorEnumProcSize, (LPARAM)&data);
	return data.size;
}
static BOOL CALLBACK _MonitorEnumProcUsableSize(HMONITOR hMonitor, HDC hdcMonitor, LPRECT lprcMonitor, LPARAM dwData) {
	EnumRectData *data = (EnumRectData *)dwData;
	if (data->count == data->screen) {
		MONITORINFO minfo;
		memset(&minfo, 0, sizeof(MONITORINFO));
		minfo.cbSize = sizeof(MONITORINFO);
		GetMonitorInfoA(hMonitor, &minfo);
		data->rect.position.x = minfo.rcWork.left;
		data->rect.position.y = minfo.rcWork.top;
		data->rect.size.x = minfo.rcWork.right - minfo.rcWork.left;
		data->rect.size.y = minfo.rcWork.bottom - minfo.rcWork.top;
	}
	data->count++;
	return TRUE;
}
static BOOL CALLBACK _MonitorEnumProcRefreshRate(HMONITOR hMonitor, HDC hdcMonitor, LPRECT lprcMonitor, LPARAM dwData) {