bethsoftvid: check return value and clean memory

CC: libav-stable@libav.org
Bug-Id: CID 733777

libavformat/bethsoftvid.c

@@ -189,6 +189,10 @@ static int read_frame(BVID_DemuxContext *vid, AVIOContext *pb, AVPacket *pkt,
     if (vid->palette) {
         uint8_t *pdata = av_packet_new_side_data(pkt, AV_PKT_DATA_PALETTE,
                                                  BVID_PALETTE_SIZE);
+        if (!pdata) {
+            ret = AVERROR(ENOMEM);
+            goto fail;
+        }
         memcpy(pdata, vid->palette, BVID_PALETTE_SIZE);
         av_freep(&vid->palette);
     }