ffmpeg.c:2916: error: Null Dereference
  pointer `mid` last assigned on line 2916 could be null and is dereferenced at line 2916, column 5.

ffmpeg.c:2908:1: start of procedure opt_metadata()
2906. }
2907. 
2908. static int opt_metadata(const char *opt, const char *arg)
      ^
2909. {
2910.     char *mid= strchr(arg, '=');

ffmpeg.c:2910:5: 
2908. static int opt_metadata(const char *opt, const char *arg)
2909. {
2910.     char *mid= strchr(arg, '=');
          ^
2911. 
2912.     if(!mid){

ffmpeg.c:2912:9: Taking true branch
2910.     char *mid= strchr(arg, '=');
2911. 
2912.     if(!mid){
              ^
2913.         fprintf(stderr, "Missing =\n");
2914.         ffmpeg_exit(1);

ffmpeg.c:2913:9: 
2911. 
2912.     if(!mid){
2913.         fprintf(stderr, "Missing =\n");
              ^
2914.         ffmpeg_exit(1);
2915.     }

ffmpeg.c:2914:9: Skipping ffmpeg_exit(): empty list of specs
2912.     if(!mid){
2913.         fprintf(stderr, "Missing =\n");
2914.         ffmpeg_exit(1);
              ^
2915.     }
2916.     *mid++= 0;

ffmpeg.c:2916:5: 
2914.         ffmpeg_exit(1);
2915.     }
2916.     *mid++= 0;
          ^
2917. 
2918.     metadata_count++;
