ffmpeg.c:2850: error: Null Dereference
  pointer `mid` last assigned on line 2850 could be null and is dereferenced at line 2850, column 5.

ffmpeg.c:2842:1: start of procedure opt_metadata()
2840. }
2841. 
2842. static int opt_metadata(const char *opt, const char *arg)
      ^
2843. {
2844.     char *mid= strchr(arg, '=');

ffmpeg.c:2844:5: 
2842. static int opt_metadata(const char *opt, const char *arg)
2843. {
2844.     char *mid= strchr(arg, '=');
          ^
2845. 
2846.     if(!mid){

ffmpeg.c:2846:9: Taking true branch
2844.     char *mid= strchr(arg, '=');
2845. 
2846.     if(!mid){
              ^
2847.         fprintf(stderr, "Missing =\n");
2848.         ffmpeg_exit(1);

ffmpeg.c:2847:9: 
2845. 
2846.     if(!mid){
2847.         fprintf(stderr, "Missing =\n");
              ^
2848.         ffmpeg_exit(1);
2849.     }

ffmpeg.c:2848:9: Skipping ffmpeg_exit(): empty list of specs
2846.     if(!mid){
2847.         fprintf(stderr, "Missing =\n");
2848.         ffmpeg_exit(1);
              ^
2849.     }
2850.     *mid++= 0;

ffmpeg.c:2850:5: 
2848.         ffmpeg_exit(1);
2849.     }
2850.     *mid++= 0;
          ^
2851. 
2852.     av_metadata_set2(&metadata, arg, mid, 0);
