ffmpeg.c:1258: error: Null Dereference
  pointer `vstats_file` last assigned on line 1248 could be null and is dereferenced by call to `fprintf()` at line 1258, column 9.

ffmpeg.c:1239:1: start of procedure do_video_stats()
1237. }
1238. 
1239. static void do_video_stats(AVFormatContext *os, AVOutputStream *ost,
      ^
1240.                            int frame_size)
1241. {

ffmpeg.c:1247:10: Taking true branch
1245. 
1246.     /* this is executed just the first time do_video_stats is called */
1247.     if (!vstats_file) {
               ^
1248.         vstats_file = fopen(vstats_filename, "w");
1249.         if (!vstats_file) {

ffmpeg.c:1248:9: 
1246.     /* this is executed just the first time do_video_stats is called */
1247.     if (!vstats_file) {
1248.         vstats_file = fopen(vstats_filename, "w");
              ^
1249.         if (!vstats_file) {
1250.             perror("fopen");

ffmpeg.c:1249:14: Taking true branch
1247.     if (!vstats_file) {
1248.         vstats_file = fopen(vstats_filename, "w");
1249.         if (!vstats_file) {
                   ^
1250.             perror("fopen");
1251.             ffmpeg_exit(1);

ffmpeg.c:1250:13: 
1248.         vstats_file = fopen(vstats_filename, "w");
1249.         if (!vstats_file) {
1250.             perror("fopen");
                  ^
1251.             ffmpeg_exit(1);
1252.         }

ffmpeg.c:1251:13: Skipping ffmpeg_exit(): empty list of specs
1249.         if (!vstats_file) {
1250.             perror("fopen");
1251.             ffmpeg_exit(1);
                  ^
1252.         }
1253.     }

ffmpeg.c:1255:5: 
1253.     }
1254. 
1255.     enc = ost->st->codec;
          ^
1256.     if (enc->codec_type == AVMEDIA_TYPE_VIDEO) {
1257.         frame_number = ost->frame_number;

ffmpeg.c:1256:9: Taking true branch
1254. 
1255.     enc = ost->st->codec;
1256.     if (enc->codec_type == AVMEDIA_TYPE_VIDEO) {
              ^
1257.         frame_number = ost->frame_number;
1258.         fprintf(vstats_file, "frame= %5d q= %2.1f ", frame_number, enc->coded_frame->quality/(float)FF_QP2LAMBDA);

ffmpeg.c:1257:9: 
1255.     enc = ost->st->codec;
1256.     if (enc->codec_type == AVMEDIA_TYPE_VIDEO) {
1257.         frame_number = ost->frame_number;
              ^
1258.         fprintf(vstats_file, "frame= %5d q= %2.1f ", frame_number, enc->coded_frame->quality/(float)FF_QP2LAMBDA);
1259.         if (enc->flags&CODEC_FLAG_PSNR)

ffmpeg.c:1258:9: 
1256.     if (enc->codec_type == AVMEDIA_TYPE_VIDEO) {
1257.         frame_number = ost->frame_number;
1258.         fprintf(vstats_file, "frame= %5d q= %2.1f ", frame_number, enc->coded_frame->quality/(float)FF_QP2LAMBDA);
              ^
1259.         if (enc->flags&CODEC_FLAG_PSNR)
1260.             fprintf(vstats_file, "PSNR= %6.2f ", psnr(enc->coded_frame->error[0]/(enc->width*enc->height*255.0*255.0)));
