libavformat: Check for malloc failures in avformat_new_stream

CC: libav-stable@libav.org
Signed-off-by: Martin Storsjö <martin@martin.st>

libavformat/utils.c

@@ -2525,6 +2525,11 @@ AVStream *avformat_new_stream(AVFormatContext *s, const AVCodec *c)
     }
 
     st->codec = avcodec_alloc_context3(c);
+    if (!st->codec) {
+        av_free(st->info);
+        av_free(st);
+        return NULL;
+    }
     if (s->iformat) {
         /* no default bitrate if decoding */
         st->codec->bit_rate = 0;