ffmpeg.c:2856: error: Null Dereference
  pointer `mid` last assigned on line 2856 could be null and is dereferenced at line 2856, column 5.

ffmpeg.c:2848:1: start of procedure opt_metadata()
2846. }
2847. 
2848. static int opt_metadata(const char *opt, const char *arg)
      ^
2849. {
2850.     char *mid= strchr(arg, '=');

ffmpeg.c:2850:5: 
2848. static int opt_metadata(const char *opt, const char *arg)
2849. {
2850.     char *mid= strchr(arg, '=');
          ^
2851. 
2852.     if(!mid){

ffmpeg.c:2852:9: Taking true branch
2850.     char *mid= strchr(arg, '=');
2851. 
2852.     if(!mid){
              ^
2853.         fprintf(stderr, "Missing =\n");
2854.         ffmpeg_exit(1);

ffmpeg.c:2853:9: 
2851. 
2852.     if(!mid){
2853.         fprintf(stderr, "Missing =\n");
              ^
2854.         ffmpeg_exit(1);
2855.     }

ffmpeg.c:2854:9: Skipping ffmpeg_exit(): empty list of specs
2852.     if(!mid){
2853.         fprintf(stderr, "Missing =\n");
2854.         ffmpeg_exit(1);
              ^
2855.     }
2856.     *mid++= 0;

ffmpeg.c:2856:5: 
2854.         ffmpeg_exit(1);
2855.     }
2856.     *mid++= 0;
          ^
2857. 
2858.     av_dict_set(&metadata, arg, mid, 0);
