ffmpeg.c:2880: error: Null Dereference
  pointer `mid` last assigned on line 2880 could be null and is dereferenced at line 2880, column 5.

ffmpeg.c:2872:1: start of procedure opt_metadata()
2870. }
2871. 
2872. static int opt_metadata(const char *opt, const char *arg)
      ^
2873. {
2874.     char *mid= strchr(arg, '=');

ffmpeg.c:2874:5: 
2872. static int opt_metadata(const char *opt, const char *arg)
2873. {
2874.     char *mid= strchr(arg, '=');
          ^
2875. 
2876.     if(!mid){

ffmpeg.c:2876:9: Taking true branch
2874.     char *mid= strchr(arg, '=');
2875. 
2876.     if(!mid){
              ^
2877.         fprintf(stderr, "Missing =\n");
2878.         ffmpeg_exit(1);

ffmpeg.c:2877:9: 
2875. 
2876.     if(!mid){
2877.         fprintf(stderr, "Missing =\n");
              ^
2878.         ffmpeg_exit(1);
2879.     }

ffmpeg.c:2878:9: Skipping ffmpeg_exit(): empty list of specs
2876.     if(!mid){
2877.         fprintf(stderr, "Missing =\n");
2878.         ffmpeg_exit(1);
              ^
2879.     }
2880.     *mid++= 0;

ffmpeg.c:2880:5: 
2878.         ffmpeg_exit(1);
2879.     }
2880.     *mid++= 0;
          ^
2881. 
2882.     metadata_count++;
