lavf/vividas: check avformat_new_stream() return

check avformat_new_stream() return.

Reviewed-by: Michael Niedermayer <michael@niedermayer.cc>
Signed-off-by: Jun Zhao <barryjzhao@tencent.com>

libavformat/vividas.c

@@ -317,6 +317,8 @@ static int track_header(VividasDemuxContext *viv, AVFormatContext *s,  uint8_t *
 
     for (i = 0; i < num_video; i++) {
         AVStream *st = avformat_new_stream(s, NULL);
+        if (!st)
+            return AVERROR(ENOMEM);
 
         st->id = i;
 
@@ -350,6 +352,8 @@ static int track_header(VividasDemuxContext *viv, AVFormatContext *s,  uint8_t *
     for(i=0;i<viv->num_audio;i++) {
         int q;
         AVStream *st = avformat_new_stream(s, NULL);
+        if (!st)
+            return AVERROR(ENOMEM);
 
         st->id = num_video + i;