MINOR: streams: Call tasklet_free() after si_release_endpoint().

Make sure we call tasklet_free() only after si_release_endpoint(), when the
unsubscribe() method has been called, so that we're sure the mux won't
attempt to access the taslet.
diff --git a/src/stream.c b/src/stream.c
index e202b87..200556f 100644
--- a/src/stream.c
+++ b/src/stream.c
@@ -398,12 +398,13 @@
 	/* applets do not release session yet */
 	must_free_sess = objt_appctx(sess->origin) && sess->origin == s->si[0].end;
 
-	tasklet_free(s->si[0].wait_event.task);
-	tasklet_free(s->si[1].wait_event.task);
 
 	si_release_endpoint(&s->si[1]);
 	si_release_endpoint(&s->si[0]);
 
+	tasklet_free(s->si[0].wait_event.task);
+	tasklet_free(s->si[1].wait_event.task);
+
 	if (must_free_sess)
 		session_free(sess);