upstream: make ssh_free(NULL) a no-op

OpenBSD-Commit-ID: 42cb285d94789cefe6608db89c63040ab0a80fa0

ssh_api.c

@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh_api.c,v 1.22 2020/10/18 11:32:02 djm Exp $ */
+/* $OpenBSD: ssh_api.c,v 1.23 2020/12/04 02:29:56 djm Exp $ */
 /*
  * Copyright (c) 2012 Markus Friedl.  All rights reserved.
  *
@@ -152,6 +152,9 @@ ssh_free(struct ssh *ssh)
 {
 	struct key_entry *k;
 
+	if (ssh == NULL)
+		return;
+
 	/*
 	 * we've only created the public keys variants in case we
 	 * are a acting as a server.