ffmpeg.c:2842: error: Null Dereference
  pointer `mid` last assigned on line 2842 could be null and is dereferenced at line 2842, column 5.

ffmpeg.c:2834:1: start of procedure opt_metadata()
2832. }
2833. 
2834. static int opt_metadata(const char *opt, const char *arg)
      ^
2835. {
2836.     char *mid= strchr(arg, '=');

ffmpeg.c:2836:5: 
2834. static int opt_metadata(const char *opt, const char *arg)
2835. {
2836.     char *mid= strchr(arg, '=');
          ^
2837. 
2838.     if(!mid){

ffmpeg.c:2838:9: Taking true branch
2836.     char *mid= strchr(arg, '=');
2837. 
2838.     if(!mid){
              ^
2839.         fprintf(stderr, "Missing =\n");
2840.         exit_program(1);

ffmpeg.c:2839:9: 
2837. 
2838.     if(!mid){
2839.         fprintf(stderr, "Missing =\n");
              ^
2840.         exit_program(1);
2841.     }

ffmpeg.c:2840:9: Skipping exit_program(): empty list of specs
2838.     if(!mid){
2839.         fprintf(stderr, "Missing =\n");
2840.         exit_program(1);
              ^
2841.     }
2842.     *mid++= 0;

ffmpeg.c:2842:5: 
2840.         exit_program(1);
2841.     }
2842.     *mid++= 0;
          ^
2843. 
2844.     av_dict_set(&metadata, arg, mid, 0);
