sctp: Use AVERROR_BUG instead of abort()

Trying to write to a stream id larger the the maximum requested is
a programming error, still there is no reason to leave a
reachable abort() in the codebase.

CC: libav-stable@libav.org

libavformat/sctp.c

@@ -297,7 +297,7 @@ static int sctp_write(URLContext *h, const uint8_t *buf, int size)
         struct sctp_sndrcvinfo info = { 0 };
         info.sinfo_stream           = AV_RB16(buf);
         if (info.sinfo_stream > s->max_streams)
-            abort();
+            return AVERROR_BUG;
         ret = ff_sctp_send(s->fd, buf + 2, size - 2, &info, MSG_EOR);
     } else
         ret = send(s->fd, buf, size, MSG_NOSIGNAL);