ffmpeg.c:2861: error: Null Dereference
  pointer `mid` last assigned on line 2861 could be null and is dereferenced at line 2861, column 5.

ffmpeg.c:2853:1: start of procedure opt_metadata()
2851. }
2852. 
2853. static int opt_metadata(const char *opt, const char *arg)
      ^
2854. {
2855.     char *mid= strchr(arg, '=');

ffmpeg.c:2855:5: 
2853. static int opt_metadata(const char *opt, const char *arg)
2854. {
2855.     char *mid= strchr(arg, '=');
          ^
2856. 
2857.     if(!mid){

ffmpeg.c:2857:9: Taking true branch
2855.     char *mid= strchr(arg, '=');
2856. 
2857.     if(!mid){
              ^
2858.         fprintf(stderr, "Missing =\n");
2859.         ffmpeg_exit(1);

ffmpeg.c:2858:9: 
2856. 
2857.     if(!mid){
2858.         fprintf(stderr, "Missing =\n");
              ^
2859.         ffmpeg_exit(1);
2860.     }

ffmpeg.c:2859:9: Skipping ffmpeg_exit(): empty list of specs
2857.     if(!mid){
2858.         fprintf(stderr, "Missing =\n");
2859.         ffmpeg_exit(1);
              ^
2860.     }
2861.     *mid++= 0;

ffmpeg.c:2861:5: 
2859.         ffmpeg_exit(1);
2860.     }
2861.     *mid++= 0;
          ^
2862. 
2863.     av_dict_set(&metadata, arg, mid, 0);
