ffmpeg.c:2867: error: Null Dereference
  pointer `mid` last assigned on line 2867 could be null and is dereferenced at line 2867, column 5.

ffmpeg.c:2859:1: start of procedure opt_metadata()
2857. }
2858. 
2859. static int opt_metadata(const char *opt, const char *arg)
      ^
2860. {
2861.     char *mid= strchr(arg, '=');

ffmpeg.c:2861:5: 
2859. static int opt_metadata(const char *opt, const char *arg)
2860. {
2861.     char *mid= strchr(arg, '=');
          ^
2862. 
2863.     if(!mid){

ffmpeg.c:2863:9: Taking true branch
2861.     char *mid= strchr(arg, '=');
2862. 
2863.     if(!mid){
              ^
2864.         fprintf(stderr, "Missing =\n");
2865.         ffmpeg_exit(1);

ffmpeg.c:2864:9: 
2862. 
2863.     if(!mid){
2864.         fprintf(stderr, "Missing =\n");
              ^
2865.         ffmpeg_exit(1);
2866.     }

ffmpeg.c:2865:9: Skipping ffmpeg_exit(): empty list of specs
2863.     if(!mid){
2864.         fprintf(stderr, "Missing =\n");
2865.         ffmpeg_exit(1);
              ^
2866.     }
2867.     *mid++= 0;

ffmpeg.c:2867:5: 
2865.         ffmpeg_exit(1);
2866.     }
2867.     *mid++= 0;
          ^
2868. 
2869.     av_dict_set(&metadata, arg, mid, 0);
