staging: rtl8192u: r8192U_core: Fix driver_info dereference as a null pointer

Fix possible use of use of driver_info as a null pointer in
query_rxdesc_status()
This could happen if stats->RxIs40MHzPacket still has the
default value of zero.
Signed-off-by: Rickard Strandqvist <rickard_strandqvist@spectrumdigital.se>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtl8192u/r8192U_core.c

@@ -4476,13 +4476,10 @@ static void query_rxdesc_status(struct sk_buff *skb,
 		skb_pull(skb, stats->RxBufShift + stats->RxDrvInfoSize);
 	}
 
-	/* for debug 2008.5.29 */
-
-	//added by vivi, for MP, 20080108
-	stats->RxIs40MHzPacket = driver_info->BW;
-	if (stats->RxDrvInfoSize != 0)
+	if (driver_info) {
+		stats->RxIs40MHzPacket = driver_info->BW;
 		TranslateRxSignalStuff819xUsb(skb, stats, driver_info);
-
+	}
 }
 
 static void rtl8192_rx_nomal(struct sk_buff *skb)