avformat/oggdec: favor av_freep() over av_free()

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

libavformat/oggdec.c

@@ -99,7 +99,7 @@ static int ogg_restore(AVFormatContext *s, int discard)
     if (!discard) {
 
         for (i = 0; i < ogg->nstreams; i++)
-            av_free(ogg->streams[i].buf);
+            av_freep(&ogg->streams[i].buf);
 
         avio_seek(bc, ost->pos, SEEK_SET);
         ogg->page_pos = -1;
@@ -633,14 +633,14 @@ static int ogg_read_close(AVFormatContext *s)
     int i;
 
     for (i = 0; i < ogg->nstreams; i++) {
-        av_free(ogg->streams[i].buf);
+        av_freep(&ogg->streams[i].buf);
         if (ogg->streams[i].codec &&
             ogg->streams[i].codec->cleanup) {
             ogg->streams[i].codec->cleanup(s, i);
         }
-        av_free(ogg->streams[i].private);
+        av_freep(&ogg->streams[i].private);
     }
-    av_free(ogg->streams);
+    av_freep(&ogg->streams);
     return 0;
 }