ffmpeg.c:2882: error: Null Dereference
  pointer `mid` last assigned on line 2882 could be null and is dereferenced at line 2882, column 5.

ffmpeg.c:2874:1: start of procedure opt_metadata()
2872. }
2873. 
2874. static int opt_metadata(const char *opt, const char *arg)
      ^
2875. {
2876.     char *mid= strchr(arg, '=');

ffmpeg.c:2876:5: 
2874. static int opt_metadata(const char *opt, const char *arg)
2875. {
2876.     char *mid= strchr(arg, '=');
          ^
2877. 
2878.     if(!mid){

ffmpeg.c:2878:9: Taking true branch
2876.     char *mid= strchr(arg, '=');
2877. 
2878.     if(!mid){
              ^
2879.         fprintf(stderr, "Missing =\n");
2880.         av_exit(1);

ffmpeg.c:2879:9: 
2877. 
2878.     if(!mid){
2879.         fprintf(stderr, "Missing =\n");
              ^
2880.         av_exit(1);
2881.     }

ffmpeg.c:2880:9: Skipping av_exit(): empty list of specs
2878.     if(!mid){
2879.         fprintf(stderr, "Missing =\n");
2880.         av_exit(1);
              ^
2881.     }
2882.     *mid++= 0;

ffmpeg.c:2882:5: 
2880.         av_exit(1);
2881.     }
2882.     *mid++= 0;
          ^
2883. 
2884.     metadata_count++;
