ffmpeg.c:2842: error: Null Dereference
  pointer `codec_tag` last assigned on line 2838 could be null and is dereferenced at line 2842, column 5.

ffmpeg.c:2833:1: start of procedure opt_codec_tag()
2831. }
2832. 
2833. static void opt_codec_tag(const char *opt, const char *arg)
      ^
2834. {
2835.     char *tail;

ffmpeg.c:2838:18: Condition is false
2836.     uint32_t *codec_tag;
2837. 
2838.     codec_tag = !strcmp(opt, "atag") ? &audio_codec_tag :
                       ^
2839.                 !strcmp(opt, "vtag") ? &video_codec_tag :
2840.                 !strcmp(opt, "stag") ? &subtitle_codec_tag : NULL;

ffmpeg.c:2839:18: Condition is false
2837. 
2838.     codec_tag = !strcmp(opt, "atag") ? &audio_codec_tag :
2839.                 !strcmp(opt, "vtag") ? &video_codec_tag :
                       ^
2840.                 !strcmp(opt, "stag") ? &subtitle_codec_tag : NULL;
2841. 

ffmpeg.c:2840:18: Condition is false
2838.     codec_tag = !strcmp(opt, "atag") ? &audio_codec_tag :
2839.                 !strcmp(opt, "vtag") ? &video_codec_tag :
2840.                 !strcmp(opt, "stag") ? &subtitle_codec_tag : NULL;
                       ^
2841. 
2842.     *codec_tag = strtol(arg, &tail, 0);

ffmpeg.c:2840:17: 
2838.     codec_tag = !strcmp(opt, "atag") ? &audio_codec_tag :
2839.                 !strcmp(opt, "vtag") ? &video_codec_tag :
2840.                 !strcmp(opt, "stag") ? &subtitle_codec_tag : NULL;
                      ^
2841. 
2842.     *codec_tag = strtol(arg, &tail, 0);

ffmpeg.c:2839:17: 
2837. 
2838.     codec_tag = !strcmp(opt, "atag") ? &audio_codec_tag :
2839.                 !strcmp(opt, "vtag") ? &video_codec_tag :
                      ^
2840.                 !strcmp(opt, "stag") ? &subtitle_codec_tag : NULL;
2841. 

ffmpeg.c:2838:17: 
2836.     uint32_t *codec_tag;
2837. 
2838.     codec_tag = !strcmp(opt, "atag") ? &audio_codec_tag :
                      ^
2839.                 !strcmp(opt, "vtag") ? &video_codec_tag :
2840.                 !strcmp(opt, "stag") ? &subtitle_codec_tag : NULL;

ffmpeg.c:2838:5: 
2836.     uint32_t *codec_tag;
2837. 
2838.     codec_tag = !strcmp(opt, "atag") ? &audio_codec_tag :
          ^
2839.                 !strcmp(opt, "vtag") ? &video_codec_tag :
2840.                 !strcmp(opt, "stag") ? &subtitle_codec_tag : NULL;

ffmpeg.c:2842:5: 
2840.                 !strcmp(opt, "stag") ? &subtitle_codec_tag : NULL;
2841. 
2842.     *codec_tag = strtol(arg, &tail, 0);
          ^
2843.     if (!tail || *tail)
2844.         *codec_tag = arg[0] + (arg[1]<<8) + (arg[2]<<16) + (arg[3]<<24);
