ffmpeg.c:2845: error: Null Dereference
  pointer `mid` last assigned on line 2845 could be null and is dereferenced at line 2845, column 5.

ffmpeg.c:2837:1: start of procedure opt_metadata()
2835. }
2836. 
2837. static int opt_metadata(const char *opt, const char *arg)
      ^
2838. {
2839.     char *mid= strchr(arg, '=');

ffmpeg.c:2839:5: 
2837. static int opt_metadata(const char *opt, const char *arg)
2838. {
2839.     char *mid= strchr(arg, '=');
          ^
2840. 
2841.     if(!mid){

ffmpeg.c:2841:9: Taking true branch
2839.     char *mid= strchr(arg, '=');
2840. 
2841.     if(!mid){
              ^
2842.         fprintf(stderr, "Missing =\n");
2843.         ffmpeg_exit(1);

ffmpeg.c:2842:9: 
2840. 
2841.     if(!mid){
2842.         fprintf(stderr, "Missing =\n");
              ^
2843.         ffmpeg_exit(1);
2844.     }

ffmpeg.c:2843:9: Skipping ffmpeg_exit(): empty list of specs
2841.     if(!mid){
2842.         fprintf(stderr, "Missing =\n");
2843.         ffmpeg_exit(1);
              ^
2844.     }
2845.     *mid++= 0;

ffmpeg.c:2845:5: 
2843.         ffmpeg_exit(1);
2844.     }
2845.     *mid++= 0;
          ^
2846. 
2847.     av_dict_set(&metadata, arg, mid, 0);
