packetizer: flac: fix memory leak

(cherry picked from commit 832510eb27f32d6e08451d7591a8149caadff935)
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

modules/packetizer/flac.c

@@ -769,6 +769,7 @@ static void Close(vlc_object_t *p_this)
     decoder_t *p_dec = (decoder_t *)p_this;
     decoder_sys_t *p_sys = p_dec->p_sys;
 
+    es_format_Clean(&p_dec->fmt_out);
     block_BytestreamRelease(&p_sys->bytestream);
     free(p_sys);
 }