nsvdec: don't ignore the return value of av_get_packet()

Fixes invalid reads with corrupted files.

CC: libav-stable@libav.org
Bug-Id: 1039

libavformat/nsvdec.c

@@ -520,6 +520,7 @@ static int nsv_read_chunk(AVFormatContext *s, int fill_header)
     uint32_t vsize;
     uint16_t asize;
     uint16_t auxsize;
+    int ret;
 
     if (nsv->ahead[0].data || nsv->ahead[1].data)
         return 0; //-1; /* hey! eat what you've in your plate first! */
@@ -571,7 +572,8 @@ null_chunk_retry:
     if (vsize && st[NSV_ST_VIDEO]) {
         nst = st[NSV_ST_VIDEO]->priv_data;
         pkt = &nsv->ahead[NSV_ST_VIDEO];
-        av_get_packet(pb, pkt, vsize);
+        if ((ret = av_get_packet(pb, pkt, vsize)) < 0)
+            return ret;
         pkt->stream_index = st[NSV_ST_VIDEO]->index;//NSV_ST_VIDEO;
         pkt->dts = nst->frame_offset;
         pkt->flags |= nsv->state == NSV_HAS_READ_NSVS ? AV_PKT_FLAG_KEY : 0; /* keyframe only likely on a sync frame */
@@ -615,7 +617,8 @@ null_chunk_retry:
                        bps, channels, samplerate);
             }
         }
-        av_get_packet(pb, pkt, asize);
+        if ((ret = av_get_packet(pb, pkt, asize)) < 0)
+            return ret;
         pkt->stream_index = st[NSV_ST_AUDIO]->index;//NSV_ST_AUDIO;
         pkt->flags |= nsv->state == NSV_HAS_READ_NSVS ? AV_PKT_FLAG_KEY : 0; /* keyframe only likely on a sync frame */
         if( nsv->state == NSV_HAS_READ_NSVS && st[NSV_ST_VIDEO] ) {