avformat/utils: free s->pb for image2 as it can be used with and without a file

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/utils.c

@@ -3548,7 +3548,7 @@ void avformat_close_input(AVFormatContext **ps)
     s  = *ps;
     pb = s->pb;
 
-    if ((s->iformat && s->iformat->flags & AVFMT_NOFILE) ||
+    if ((s->iformat && strcmp(s->iformat->name, "image2") && s->iformat->flags & AVFMT_NOFILE) ||
         (s->flags & AVFMT_FLAG_CUSTOM_IO))
         pb = NULL;