ffmpeg.c:2913: error: Null Dereference
  pointer `mid` last assigned on line 2913 could be null and is dereferenced at line 2913, column 5.

ffmpeg.c:2905:1: start of procedure opt_metadata()
2903. }
2904. 
2905. static int opt_metadata(const char *opt, const char *arg)
      ^
2906. {
2907.     char *mid= strchr(arg, '=');

ffmpeg.c:2907:5: 
2905. static int opt_metadata(const char *opt, const char *arg)
2906. {
2907.     char *mid= strchr(arg, '=');
          ^
2908. 
2909.     if(!mid){

ffmpeg.c:2909:9: Taking true branch
2907.     char *mid= strchr(arg, '=');
2908. 
2909.     if(!mid){
              ^
2910.         fprintf(stderr, "Missing =\n");
2911.         ffmpeg_exit(1);

ffmpeg.c:2910:9: 
2908. 
2909.     if(!mid){
2910.         fprintf(stderr, "Missing =\n");
              ^
2911.         ffmpeg_exit(1);
2912.     }

ffmpeg.c:2911:9: Skipping ffmpeg_exit(): empty list of specs
2909.     if(!mid){
2910.         fprintf(stderr, "Missing =\n");
2911.         ffmpeg_exit(1);
              ^
2912.     }
2913.     *mid++= 0;

ffmpeg.c:2913:5: 
2911.         ffmpeg_exit(1);
2912.     }
2913.     *mid++= 0;
          ^
2914. 
2915.     metadata_count++;
