ffmpeg.c:2568: error: Null Dereference
  pointer `mid` last assigned on line 2568 could be null and is dereferenced at line 2568, column 5.

ffmpeg.c:2560:1: start of procedure opt_metadata()
2558. }
2559. 
2560. static int opt_metadata(const char *opt, const char *arg)
      ^
2561. {
2562.     char *mid= strchr(arg, '=');

ffmpeg.c:2562:5: 
2560. static int opt_metadata(const char *opt, const char *arg)
2561. {
2562.     char *mid= strchr(arg, '=');
          ^
2563. 
2564.     if(!mid){

ffmpeg.c:2564:9: Taking true branch
2562.     char *mid= strchr(arg, '=');
2563. 
2564.     if(!mid){
              ^
2565.         fprintf(stderr, "Missing =\n");
2566.         av_exit(1);

ffmpeg.c:2565:9: 
2563. 
2564.     if(!mid){
2565.         fprintf(stderr, "Missing =\n");
              ^
2566.         av_exit(1);
2567.     }

ffmpeg.c:2566:9: Skipping av_exit(): empty list of specs
2564.     if(!mid){
2565.         fprintf(stderr, "Missing =\n");
2566.         av_exit(1);
              ^
2567.     }
2568.     *mid++= 0;

ffmpeg.c:2568:5: 
2566.         av_exit(1);
2567.     }
2568.     *mid++= 0;
          ^
2569. 
2570.     metadata_count++;
