avformat/rtsp: break on unknown protocols

This function needs more cleanup and it lacks error handling

Fixes: use of uninitialized memory
Fixes: CID700776

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/rtsp.c

@@ -949,6 +949,8 @@ static void rtsp_parse_transport(AVFormatContext *s,
                              ";,", &p);
             }
             th->transport = RTSP_TRANSPORT_RAW;
+        } else {
+            break;
         }
         if (!av_strcasecmp(lower_transport, "TCP"))
             th->lower_transport = RTSP_LOWER_TRANSPORT_TCP;