lavf/concatdec: avoid leaking URLs.

Use av_realloc instead of av_realloc_f to keep the original
array in case of failure: it is freed in full by the fail label.

libavformat/concatdec.c

@@ -69,9 +69,11 @@ static int add_file(AVFormatContext *avf, char *filename, ConcatFile **rfile,
 
     if (cat->nb_files >= *nb_files_alloc) {
         unsigned n = FFMAX(*nb_files_alloc * 2, 16);
-        if (n <= cat->nb_files ||
-            !(cat->files = av_realloc_f(cat->files, n, sizeof(*cat->files))))
+        ConcatFile *new_files;
+        if (n <= cat->nb_files || n > SIZE_MAX / sizeof(*cat->files) ||
+            !(new_files = av_realloc(cat->files, n * sizeof(*cat->files))))
             return AVERROR(ENOMEM);
+        cat->files = new_files;
         *nb_files_alloc = n;
     }