ffserver: Replace one malloc(AVStream) by avformat_new_stream()

This fixes a null pointer dereference from the recently introduced
AVStream->internal
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

ffserver.c

@@ -3331,6 +3331,7 @@ static int rtp_new_av_stream(HTTPContext *c,
     URLContext *h = NULL;
     uint8_t *dummy_buf;
     int max_packet_size;
+    void *st_internal;
 
     /* now we can open the relevant output stream */
     ctx = avformat_alloc_context();
@@ -3338,14 +3339,13 @@ static int rtp_new_av_stream(HTTPContext *c,
         return -1;
     ctx->oformat = av_guess_format("rtp", NULL, NULL);
 
-    st = av_mallocz(sizeof(AVStream));
+    st = avformat_new_stream(ctx, NULL);
     if (!st)
         goto fail;
-    ctx->nb_streams = 1;
-    ctx->streams = av_mallocz_array(ctx->nb_streams, sizeof(AVStream *));
-    if (!ctx->streams)
-      goto fail;
-    ctx->streams[0] = st;
+
+    av_freep(&st->codec);
+    av_freep(&st->info);
+    st_internal = st->internal;
 
     if (!c->stream->feed ||
         c->stream->feed == c->stream)
@@ -3355,6 +3355,7 @@ static int rtp_new_av_stream(HTTPContext *c,
                c->stream->feed->streams[c->stream->feed_streams[stream_index]],
                sizeof(AVStream));
     st->priv_data = NULL;
+    st->internal = st_internal;
 
     /* build destination RTP address */
     ipaddr = inet_ntoa(dest_addr->sin_addr);