ffmpeg.c:1026: error: Null Dereference
  pointer `vstats_file` last assigned on line 1016 could be null and is dereferenced by call to `fprintf()` at line 1026, column 9.

ffmpeg.c:1007:1: start of procedure do_video_stats()
1005. }
1006. 
1007. static void do_video_stats(AVFormatContext *os, AVOutputStream *ost,
      ^
1008.                            int frame_size)
1009. {

ffmpeg.c:1015:10: Taking true branch
1013. 
1014.     /* this is executed just the first time do_video_stats is called */
1015.     if (!vstats_file) {
               ^
1016.         vstats_file = fopen(vstats_filename, "w");
1017.         if (!vstats_file) {

ffmpeg.c:1016:9: 
1014.     /* this is executed just the first time do_video_stats is called */
1015.     if (!vstats_file) {
1016.         vstats_file = fopen(vstats_filename, "w");
              ^
1017.         if (!vstats_file) {
1018.             perror("fopen");

ffmpeg.c:1017:14: Taking true branch
1015.     if (!vstats_file) {
1016.         vstats_file = fopen(vstats_filename, "w");
1017.         if (!vstats_file) {
                   ^
1018.             perror("fopen");
1019.             av_exit(1);

ffmpeg.c:1018:13: 
1016.         vstats_file = fopen(vstats_filename, "w");
1017.         if (!vstats_file) {
1018.             perror("fopen");
                  ^
1019.             av_exit(1);
1020.         }

ffmpeg.c:1019:13: Skipping av_exit(): empty list of specs
1017.         if (!vstats_file) {
1018.             perror("fopen");
1019.             av_exit(1);
                  ^
1020.         }
1021.     }

ffmpeg.c:1023:5: 
1021.     }
1022. 
1023.     enc = ost->st->codec;
          ^
1024.     if (enc->codec_type == CODEC_TYPE_VIDEO) {
1025.         frame_number = ost->frame_number;

ffmpeg.c:1024:9: Taking true branch
1022. 
1023.     enc = ost->st->codec;
1024.     if (enc->codec_type == CODEC_TYPE_VIDEO) {
              ^
1025.         frame_number = ost->frame_number;
1026.         fprintf(vstats_file, "frame= %5d q= %2.1f ", frame_number, enc->coded_frame->quality/(float)FF_QP2LAMBDA);

ffmpeg.c:1025:9: 
1023.     enc = ost->st->codec;
1024.     if (enc->codec_type == CODEC_TYPE_VIDEO) {
1025.         frame_number = ost->frame_number;
              ^
1026.         fprintf(vstats_file, "frame= %5d q= %2.1f ", frame_number, enc->coded_frame->quality/(float)FF_QP2LAMBDA);
1027.         if (enc->flags&CODEC_FLAG_PSNR)

ffmpeg.c:1026:9: 
1024.     if (enc->codec_type == CODEC_TYPE_VIDEO) {
1025.         frame_number = ost->frame_number;
1026.         fprintf(vstats_file, "frame= %5d q= %2.1f ", frame_number, enc->coded_frame->quality/(float)FF_QP2LAMBDA);
              ^
1027.         if (enc->flags&CODEC_FLAG_PSNR)
1028.             fprintf(vstats_file, "PSNR= %6.2f ", psnr(enc->coded_frame->error[0]/(enc->width*enc->height*255.0*255.0)));
