rtsp: Make sure we don't write too many transport entries into a fixed-size array

(cherry picked from commit b90adb0a)
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/rtsp.c

@@ -931,6 +931,8 @@ static void rtsp_parse_transport(RTSPMessageHeader *reply, const char *p)
             p++;
 
         reply->nb_transports++;
+        if (reply->nb_transports >= RTSP_MAX_TRANSPORTS)
+            break;
     }
 }