ffmpeg.c:2865: error: Null Dereference
  pointer `mid` last assigned on line 2865 could be null and is dereferenced at line 2865, column 5.

ffmpeg.c:2857:1: start of procedure opt_metadata()
2855. }
2856. 
2857. static int opt_metadata(const char *opt, const char *arg)
      ^
2858. {
2859.     char *mid= strchr(arg, '=');

ffmpeg.c:2859:5: 
2857. static int opt_metadata(const char *opt, const char *arg)
2858. {
2859.     char *mid= strchr(arg, '=');
          ^
2860. 
2861.     if(!mid){

ffmpeg.c:2861:9: Taking true branch
2859.     char *mid= strchr(arg, '=');
2860. 
2861.     if(!mid){
              ^
2862.         fprintf(stderr, "Missing =\n");
2863.         ffmpeg_exit(1);

ffmpeg.c:2862:9: 
2860. 
2861.     if(!mid){
2862.         fprintf(stderr, "Missing =\n");
              ^
2863.         ffmpeg_exit(1);
2864.     }

ffmpeg.c:2863:9: Skipping ffmpeg_exit(): empty list of specs
2861.     if(!mid){
2862.         fprintf(stderr, "Missing =\n");
2863.         ffmpeg_exit(1);
              ^
2864.     }
2865.     *mid++= 0;

ffmpeg.c:2865:5: 
2863.         ffmpeg_exit(1);
2864.     }
2865.     *mid++= 0;
          ^
2866. 
2867.     av_dict_set(&metadata, arg, mid, 0);
