ffmpeg.c:3630: error: Null Dereference
  pointer `st` last assigned on line 3624 could be null and is dereferenced at line 3630, column 20.

ffmpeg.c:3616:1: start of procedure new_subtitle_stream()
3614. }
3615. 
3616. static void new_subtitle_stream(AVFormatContext *oc, int file_idx)
      ^
3617. {
3618.     AVStream *st;

ffmpeg.c:3620:5: 
3618.     AVStream *st;
3619.     AVOutputStream *ost;
3620.     AVCodec *codec=NULL;
          ^
3621.     AVCodecContext *subtitle_enc;
3622.     enum CodecID codec_id = CODEC_ID_NONE;

ffmpeg.c:3622:5: 
3620.     AVCodec *codec=NULL;
3621.     AVCodecContext *subtitle_enc;
3622.     enum CodecID codec_id = CODEC_ID_NONE;
          ^
3623. 
3624.     st = av_new_stream(oc, oc->nb_streams < nb_streamid_map ? streamid_map[oc->nb_streams] : 0);

ffmpeg.c:3624:28: Condition is true
3622.     enum CodecID codec_id = CODEC_ID_NONE;
3623. 
3624.     st = av_new_stream(oc, oc->nb_streams < nb_streamid_map ? streamid_map[oc->nb_streams] : 0);
                                 ^
3625.     if (!st) {
3626.         fprintf(stderr, "Could not alloc stream\n");

ffmpeg.c:3624:5: 
3622.     enum CodecID codec_id = CODEC_ID_NONE;
3623. 
3624.     st = av_new_stream(oc, oc->nb_streams < nb_streamid_map ? streamid_map[oc->nb_streams] : 0);
          ^
3625.     if (!st) {
3626.         fprintf(stderr, "Could not alloc stream\n");

libavformat/utils.c:2585:1: start of procedure av_new_stream()
  2583. }
  2584. 
  2585. AVStream *av_new_stream(AVFormatContext *s, int id)
        ^
  2586. {
  2587.     AVStream *st;

libavformat/utils.c:2591:9: Taking true branch
  2589.     AVStream **streams;
  2590. 
  2591.     if (s->nb_streams >= INT_MAX/sizeof(*streams))
                ^
  2592.         return NULL;
  2593.     streams = av_realloc(s->streams, (s->nb_streams + 1) * sizeof(*streams));

libavformat/utils.c:2592:9: 
  2590. 
  2591.     if (s->nb_streams >= INT_MAX/sizeof(*streams))
  2592.         return NULL;
                ^
  2593.     streams = av_realloc(s->streams, (s->nb_streams + 1) * sizeof(*streams));
  2594.     if (!streams)

libavformat/utils.c:2634:1: return from a call to av_new_stream
  2632.     s->streams[s->nb_streams++] = st;
  2633.     return st;
  2634. }
        ^
  2635. 
  2636. AVProgram *av_new_program(AVFormatContext *ac, int id)

ffmpeg.c:3625:10: Taking true branch
3623. 
3624.     st = av_new_stream(oc, oc->nb_streams < nb_streamid_map ? streamid_map[oc->nb_streams] : 0);
3625.     if (!st) {
               ^
3626.         fprintf(stderr, "Could not alloc stream\n");
3627.         ffmpeg_exit(1);

ffmpeg.c:3626:9: 
3624.     st = av_new_stream(oc, oc->nb_streams < nb_streamid_map ? streamid_map[oc->nb_streams] : 0);
3625.     if (!st) {
3626.         fprintf(stderr, "Could not alloc stream\n");
              ^
3627.         ffmpeg_exit(1);
3628.     }

ffmpeg.c:3627:9: Skipping ffmpeg_exit(): empty list of specs
3625.     if (!st) {
3626.         fprintf(stderr, "Could not alloc stream\n");
3627.         ffmpeg_exit(1);
              ^
3628.     }
3629.     ost = new_output_stream(oc, file_idx);

ffmpeg.c:3629:5: Skipping new_output_stream(): empty list of specs
3627.         ffmpeg_exit(1);
3628.     }
3629.     ost = new_output_stream(oc, file_idx);
          ^
3630.     subtitle_enc = st->codec;
3631.     output_codecs = grow_array(output_codecs, sizeof(*output_codecs), &nb_output_codecs, nb_output_codecs + 1);

ffmpeg.c:3630:5: 
3628.     }
3629.     ost = new_output_stream(oc, file_idx);
3630.     subtitle_enc = st->codec;
          ^
3631.     output_codecs = grow_array(output_codecs, sizeof(*output_codecs), &nb_output_codecs, nb_output_codecs + 1);
3632.     if(!subtitle_stream_copy){
