avcodec/libfdk-aacdec: use av_feeep() to avoid leaving stale pointers in memory

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

libavcodec/libfdk-aacdec.c

@@ -177,8 +177,8 @@ static av_cold int fdk_aac_decode_close(AVCodecContext *avctx)
 
     if (s->handle)
         aacDecoder_Close(s->handle);
-    av_free(s->decoder_buffer);
-    av_free(s->anc_buffer);
+    av_freep(&s->decoder_buffer);
+    av_freep(&s->anc_buffer);
 
     return 0;
 }