lavf/utils.c: Avoid a null pointer dereference on oom after duration_error allocation.

libavformat/utils.c

@@ -2857,6 +2857,8 @@ int avformat_find_stream_info(AVFormatContext *ic, AVDictionary **options)
 
                 if (!st->info->duration_error)
                     st->info->duration_error = av_mallocz(sizeof(st->info->duration_error[0])*2);
+                if (!st->info->duration_error)
+                    return AVERROR(ENOMEM);
 
 //                 if(st->codec->codec_type == AVMEDIA_TYPE_VIDEO)
 //                     av_log(NULL, AV_LOG_ERROR, "%f\n", dts);