ffmpeg.c:2784: error: Null Dereference
  pointer `mid` last assigned on line 2784 could be null and is dereferenced at line 2784, column 5.

ffmpeg.c:2776:1: start of procedure opt_metadata()
2774. }
2775. 
2776. static int opt_metadata(const char *opt, const char *arg)
      ^
2777. {
2778.     char *mid= strchr(arg, '=');

ffmpeg.c:2778:5: 
2776. static int opt_metadata(const char *opt, const char *arg)
2777. {
2778.     char *mid= strchr(arg, '=');
          ^
2779. 
2780.     if(!mid){

ffmpeg.c:2780:9: Taking true branch
2778.     char *mid= strchr(arg, '=');
2779. 
2780.     if(!mid){
              ^
2781.         fprintf(stderr, "Missing =\n");
2782.         ffmpeg_exit(1);

ffmpeg.c:2781:9: 
2779. 
2780.     if(!mid){
2781.         fprintf(stderr, "Missing =\n");
              ^
2782.         ffmpeg_exit(1);
2783.     }

ffmpeg.c:2782:9: Skipping ffmpeg_exit(): empty list of specs
2780.     if(!mid){
2781.         fprintf(stderr, "Missing =\n");
2782.         ffmpeg_exit(1);
              ^
2783.     }
2784.     *mid++= 0;

ffmpeg.c:2784:5: 
2782.         ffmpeg_exit(1);
2783.     }
2784.     *mid++= 0;
          ^
2785. 
2786.     av_metadata_set2(&metadata, arg, mid, 0);
