ffmpeg.c:2821: error: Null Dereference
  pointer `mid` last assigned on line 2821 could be null and is dereferenced at line 2821, column 5.

ffmpeg.c:2813:1: start of procedure opt_metadata()
2811. }
2812. 
2813. static int opt_metadata(const char *opt, const char *arg)
      ^
2814. {
2815.     char *mid= strchr(arg, '=');

ffmpeg.c:2815:5: 
2813. static int opt_metadata(const char *opt, const char *arg)
2814. {
2815.     char *mid= strchr(arg, '=');
          ^
2816. 
2817.     if(!mid){

ffmpeg.c:2817:9: Taking true branch
2815.     char *mid= strchr(arg, '=');
2816. 
2817.     if(!mid){
              ^
2818.         fprintf(stderr, "Missing =\n");
2819.         ffmpeg_exit(1);

ffmpeg.c:2818:9: 
2816. 
2817.     if(!mid){
2818.         fprintf(stderr, "Missing =\n");
              ^
2819.         ffmpeg_exit(1);
2820.     }

ffmpeg.c:2819:9: Skipping ffmpeg_exit(): empty list of specs
2817.     if(!mid){
2818.         fprintf(stderr, "Missing =\n");
2819.         ffmpeg_exit(1);
              ^
2820.     }
2821.     *mid++= 0;

ffmpeg.c:2821:5: 
2819.         ffmpeg_exit(1);
2820.     }
2821.     *mid++= 0;
          ^
2822. 
2823.     av_metadata_set2(&metadata, arg, mid, 0);

static int opt_metadata(const char *opt, const char *arg)
{
    char *mid= strchr(arg, '=');
    if(!mid){
        fprintf(stderr, "Missing =\n");
        ffmpeg_exit(1);
    }
    *mid++= 0;
    av_metadata_set2(&metadata, arg, mid, 0);
    return 0;
}
['static int opt_metadata(const char *opt, const char *arg)\n{\n    char *mid= strchr(arg, \'=\');\n    if(!mid){\n        fprintf(stderr, "Missing =\\n");\n        ffmpeg_exit(1);\n    }\n    *mid++= 0;\n    av_metadata_set2(&metadata, arg, mid, 0);\n    return 0;\n}']