avcodec/eatqi: use av_freep(), do not leave stale pointers in memory

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

libavcodec/eatqi.c

@@ -149,7 +149,7 @@ static int tqi_decode_frame(AVCodecContext *avctx,
 static av_cold int tqi_decode_end(AVCodecContext *avctx)
 {
     TqiContext *t = avctx->priv_data;
-    av_free(t->bitstream_buf);
+    av_freep(&t->bitstream_buf);
     return 0;
 }