ffmpeg.c:2915: error: Null Dereference
  pointer `mid` last assigned on line 2915 could be null and is dereferenced at line 2915, column 5.

ffmpeg.c:2907:1: start of procedure opt_metadata()
2905. }
2906. 
2907. static int opt_metadata(const char *opt, const char *arg)
      ^
2908. {
2909.     char *mid= strchr(arg, '=');

ffmpeg.c:2909:5: 
2907. static int opt_metadata(const char *opt, const char *arg)
2908. {
2909.     char *mid= strchr(arg, '=');
          ^
2910. 
2911.     if(!mid){

ffmpeg.c:2911:9: Taking true branch
2909.     char *mid= strchr(arg, '=');
2910. 
2911.     if(!mid){
              ^
2912.         fprintf(stderr, "Missing =\n");
2913.         ffmpeg_exit(1);

ffmpeg.c:2912:9: 
2910. 
2911.     if(!mid){
2912.         fprintf(stderr, "Missing =\n");
              ^
2913.         ffmpeg_exit(1);
2914.     }

ffmpeg.c:2913:9: Skipping ffmpeg_exit(): empty list of specs
2911.     if(!mid){
2912.         fprintf(stderr, "Missing =\n");
2913.         ffmpeg_exit(1);
              ^
2914.     }
2915.     *mid++= 0;

ffmpeg.c:2915:5: 
2913.         ffmpeg_exit(1);
2914.     }
2915.     *mid++= 0;
          ^
2916. 
2917.     metadata_count++;
