ffmpeg.c:1028: error: Null Dereference
  pointer `vstats_file` last assigned on line 1018 could be null and is dereferenced by call to `fprintf()` at line 1028, column 9.

ffmpeg.c:1009:1: start of procedure do_video_stats()
1007. }
1008. 
1009. static void do_video_stats(AVFormatContext *os, AVOutputStream *ost,
      ^
1010.                            int frame_size)
1011. {

ffmpeg.c:1017:10: Taking true branch
1015. 
1016.     /* this is executed just the first time do_video_stats is called */
1017.     if (!vstats_file) {
               ^
1018.         vstats_file = fopen(vstats_filename, "w");
1019.         if (!vstats_file) {

ffmpeg.c:1018:9: 
1016.     /* this is executed just the first time do_video_stats is called */
1017.     if (!vstats_file) {
1018.         vstats_file = fopen(vstats_filename, "w");
              ^
1019.         if (!vstats_file) {
1020.             perror("fopen");

ffmpeg.c:1019:14: Taking true branch
1017.     if (!vstats_file) {
1018.         vstats_file = fopen(vstats_filename, "w");
1019.         if (!vstats_file) {
                   ^
1020.             perror("fopen");
1021.             av_exit(1);

ffmpeg.c:1020:13: 
1018.         vstats_file = fopen(vstats_filename, "w");
1019.         if (!vstats_file) {
1020.             perror("fopen");
                  ^
1021.             av_exit(1);
1022.         }

ffmpeg.c:1021:13: Skipping av_exit(): empty list of specs
1019.         if (!vstats_file) {
1020.             perror("fopen");
1021.             av_exit(1);
                  ^
1022.         }
1023.     }

ffmpeg.c:1025:5: 
1023.     }
1024. 
1025.     enc = ost->st->codec;
          ^
1026.     if (enc->codec_type == CODEC_TYPE_VIDEO) {
1027.         frame_number = ost->frame_number;

ffmpeg.c:1026:9: Taking true branch
1024. 
1025.     enc = ost->st->codec;
1026.     if (enc->codec_type == CODEC_TYPE_VIDEO) {
              ^
1027.         frame_number = ost->frame_number;
1028.         fprintf(vstats_file, "frame= %5d q= %2.1f ", frame_number, enc->coded_frame->quality/(float)FF_QP2LAMBDA);

ffmpeg.c:1027:9: 
1025.     enc = ost->st->codec;
1026.     if (enc->codec_type == CODEC_TYPE_VIDEO) {
1027.         frame_number = ost->frame_number;
              ^
1028.         fprintf(vstats_file, "frame= %5d q= %2.1f ", frame_number, enc->coded_frame->quality/(float)FF_QP2LAMBDA);
1029.         if (enc->flags&CODEC_FLAG_PSNR)

ffmpeg.c:1028:9: 
1026.     if (enc->codec_type == CODEC_TYPE_VIDEO) {
1027.         frame_number = ost->frame_number;
1028.         fprintf(vstats_file, "frame= %5d q= %2.1f ", frame_number, enc->coded_frame->quality/(float)FF_QP2LAMBDA);
              ^
1029.         if (enc->flags&CODEC_FLAG_PSNR)
1030.             fprintf(vstats_file, "PSNR= %6.2f ", psnr(enc->coded_frame->error[0]/(enc->width*enc->height*255.0*255.0)));
