Fix a bug where a pointer was cached to an array that might later move due to

source/patched-ffmpeg/libavformat/matroskadec.c

 /*
  * Matroska file demuxer
  * Copyright (c) 2003-2008 The FFmpeg Project
  *
  * This file is part of FFmpeg.
  *
  * FFmpeg is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either
  * version 2.1 of the License, or (at your option) any later version.
@@ skipping 1223 matching lines @@
     avio_seek(matroska->ctx->pb, before_pos, SEEK_SET);
     matroska->level_up = level_up;
     matroska->current_id = saved_id;
 
     return ret;
 }
 
 static void matroska_execute_seekhead(MatroskaDemuxContext *matroska)
 {
     EbmlList *seekhead_list = &matroska->seekhead;
-    MatroskaSeekhead *seekhead = seekhead_list->elem;
     int64_t before_pos = avio_tell(matroska->ctx->pb);
     int i;
 
     // we should not do any seeking in the streaming case
     if (!matroska->ctx->pb->seekable ||
         (matroska->ctx->flags & AVFMT_FLAG_IGNIDX))
         return;
 
     for (i = 0; i < seekhead_list->nb_elem; i++) {
+        MatroskaSeekhead *seekhead = seekhead_list->elem;
         if (seekhead[i].pos <= before_pos)
             continue;
 
         // defer cues parsing until we actually need cue data.
         if (seekhead[i].id == MATROSKA_ID_CUES) {
             matroska->cues_parsing_deferred = 1;
             continue;
         }
 
         if (matroska_parse_seekhead_entry(matroska, i) < 0)
@@ skipping 910 matching lines @@
 AVInputFormat ff_matroska_demuxer = {
     "matroska,webm",
     NULL_IF_CONFIG_SMALL("Matroska/WebM file format"),
     sizeof(MatroskaDemuxContext),
     matroska_probe,
     matroska_read_header,
     matroska_read_packet,
     matroska_read_close,
     matroska_read_seek,
 };