ffmpeg.c:2635: error: Null Dereference
  pointer `mid` last assigned on line 2635 could be null and is dereferenced at line 2635, column 5.

ffmpeg.c:2627:1: start of procedure opt_metadata()
2625. }
2626. 
2627. static int opt_metadata(const char *opt, const char *arg)
      ^
2628. {
2629.     char *mid= strchr(arg, '=');

ffmpeg.c:2629:5: 
2627. static int opt_metadata(const char *opt, const char *arg)
2628. {
2629.     char *mid= strchr(arg, '=');
          ^
2630. 
2631.     if(!mid){

ffmpeg.c:2631:9: Taking true branch
2629.     char *mid= strchr(arg, '=');
2630. 
2631.     if(!mid){
              ^
2632.         fprintf(stderr, "Missing =\n");
2633.         av_exit(1);

ffmpeg.c:2632:9: 
2630. 
2631.     if(!mid){
2632.         fprintf(stderr, "Missing =\n");
              ^
2633.         av_exit(1);
2634.     }

ffmpeg.c:2633:9: Skipping av_exit(): empty list of specs
2631.     if(!mid){
2632.         fprintf(stderr, "Missing =\n");
2633.         av_exit(1);
              ^
2634.     }
2635.     *mid++= 0;

ffmpeg.c:2635:5: 
2633.         av_exit(1);
2634.     }
2635.     *mid++= 0;
          ^
2636. 
2637.     metadata_count++;
