fix ffserver's SIGSEGV

ffmpeg.c

@@ -703,6 +703,7 @@ static int read_ffserver_streams(AVFormatContext *s, const char *filename)
         return err;
     /* copy stream format */
     s->nb_streams = 0;
+    s->streams = av_mallocz(sizeof(*s->streams) * ic->nb_streams);
     for(i=0;i<ic->nb_streams;i++) {
         AVStream *st;
         AVCodec *codec;

ffserver.c

@@ -2229,6 +2229,7 @@ static int http_prepare_data(HTTPContext *c)
         av_metadata_set2(&c->fmt_ctx.metadata, "copyright", c->stream->copyright, 0);
         av_metadata_set2(&c->fmt_ctx.metadata, "title"    , c->stream->title    , 0);
 
+        c->fmt_ctx.streams = av_mallocz(sizeof(*c->fmt_ctx.streams) * c->stream->nb_streams);
         for(i=0;i<c->stream->nb_streams;i++) {
             AVStream *st;
             AVStream *src;