qtsound: fix memleak (close #13416)

(cherry picked from commit 8f30f623bae32f8826aa7e7a1b6259765b901ab5)
Signed-off-by: Felix Paul Kühne <fkuehne@videolan.org>

modules/access/qtsound.m

@@ -519,6 +519,8 @@ static int Demux(demux_t *p_demux)
 
     if (p_blocka) {
         if (!p_blocka->i_pts) {
+            block_Release(p_blocka);
+
             // Nothing to transfer yet, just forget
             msleep(10000);
             return 1;