ffmpeg.c:2852: error: Null Dereference
  pointer `mid` last assigned on line 2852 could be null and is dereferenced at line 2852, column 5.

ffmpeg.c:2844:1: start of procedure opt_metadata()
2842. }
2843. 
2844. static int opt_metadata(const char *opt, const char *arg)
      ^
2845. {
2846.     char *mid= strchr(arg, '=');

ffmpeg.c:2846:5: 
2844. static int opt_metadata(const char *opt, const char *arg)
2845. {
2846.     char *mid= strchr(arg, '=');
          ^
2847. 
2848.     if(!mid){

ffmpeg.c:2848:9: Taking true branch
2846.     char *mid= strchr(arg, '=');
2847. 
2848.     if(!mid){
              ^
2849.         fprintf(stderr, "Missing =\n");
2850.         ffmpeg_exit(1);

ffmpeg.c:2849:9: 
2847. 
2848.     if(!mid){
2849.         fprintf(stderr, "Missing =\n");
              ^
2850.         ffmpeg_exit(1);
2851.     }

ffmpeg.c:2850:9: Skipping ffmpeg_exit(): empty list of specs
2848.     if(!mid){
2849.         fprintf(stderr, "Missing =\n");
2850.         ffmpeg_exit(1);
              ^
2851.     }
2852.     *mid++= 0;

ffmpeg.c:2852:5: 
2850.         ffmpeg_exit(1);
2851.     }
2852.     *mid++= 0;
          ^
2853. 
2854.     av_metadata_set2(&metadata, arg, mid, 0);
