ffmpeg.c:2626: error: Null Dereference
  pointer `mid` last assigned on line 2626 could be null and is dereferenced at line 2626, column 5.

ffmpeg.c:2618:1: start of procedure opt_metadata()
2616. }
2617. 
2618. static int opt_metadata(const char *opt, const char *arg)
      ^
2619. {
2620.     char *mid= strchr(arg, '=');

ffmpeg.c:2620:5: 
2618. static int opt_metadata(const char *opt, const char *arg)
2619. {
2620.     char *mid= strchr(arg, '=');
          ^
2621. 
2622.     if(!mid){

ffmpeg.c:2622:9: Taking true branch
2620.     char *mid= strchr(arg, '=');
2621. 
2622.     if(!mid){
              ^
2623.         fprintf(stderr, "Missing =\n");
2624.         av_exit(1);

ffmpeg.c:2623:9: 
2621. 
2622.     if(!mid){
2623.         fprintf(stderr, "Missing =\n");
              ^
2624.         av_exit(1);
2625.     }

ffmpeg.c:2624:9: Skipping av_exit(): empty list of specs
2622.     if(!mid){
2623.         fprintf(stderr, "Missing =\n");
2624.         av_exit(1);
              ^
2625.     }
2626.     *mid++= 0;

ffmpeg.c:2626:5: 
2624.         av_exit(1);
2625.     }
2626.     *mid++= 0;
          ^
2627. 
2628.     metadata_count++;
