usb: usb251xb: fix to avoid potential NULL pointer dereference

of_match_device in usb251xb_probe can fail and returns a NULL pointer.
The patch avoids a potential NULL pointer dereference in this scenario.
Signed-off-by: Aditya Pakki <pakki001@umn.edu>
Reviewed-by: Richard Leitner <richard.leitner@skidata.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/misc/usb251xb.c

@@ -612,7 +612,7 @@ static int usb251xb_probe(struct usb251xb *hub)
 							   dev);
 	int err;
 
-	if (np) {
+	if (np && of_id) {
 		err = usb251xb_get_ofdata(hub,
 					  (struct usb251xb_data *)of_id->data);
 		if (err) {