ffmpeg.c:2854: error: Null Dereference
  pointer `mid` last assigned on line 2854 could be null and is dereferenced at line 2854, column 5.

ffmpeg.c:2846:1: start of procedure opt_metadata()
2844. }
2845. 
2846. static int opt_metadata(const char *opt, const char *arg)
      ^
2847. {
2848.     char *mid= strchr(arg, '=');

ffmpeg.c:2848:5: 
2846. static int opt_metadata(const char *opt, const char *arg)
2847. {
2848.     char *mid= strchr(arg, '=');
          ^
2849. 
2850.     if(!mid){

ffmpeg.c:2850:9: Taking true branch
2848.     char *mid= strchr(arg, '=');
2849. 
2850.     if(!mid){
              ^
2851.         fprintf(stderr, "Missing =\n");
2852.         ffmpeg_exit(1);

ffmpeg.c:2851:9: 
2849. 
2850.     if(!mid){
2851.         fprintf(stderr, "Missing =\n");
              ^
2852.         ffmpeg_exit(1);
2853.     }

ffmpeg.c:2852:9: Skipping ffmpeg_exit(): empty list of specs
2850.     if(!mid){
2851.         fprintf(stderr, "Missing =\n");
2852.         ffmpeg_exit(1);
              ^
2853.     }
2854.     *mid++= 0;

ffmpeg.c:2854:5: 
2852.         ffmpeg_exit(1);
2853.     }
2854.     *mid++= 0;
          ^
2855. 
2856.     av_metadata_set2(&metadata, arg, mid, 0);
