pkcs11: Do not crash with invalid paths in ssh-agent (#1868996)

openssh-8.0p1-pkcs11-uri.patch

@@ -1216,7 +1216,7 @@ new file mode 100644
 index 00000000..e1a7b4e0
 --- /dev/null
 +++ b/ssh-pkcs11-uri.c
-@@ -0,0 +1,421 @@
+@@ -0,0 +1,425 @@
 +/*
 + * Copyright (c) 2017 Red Hat
 + *
@@ -1468,6 +1468,10 @@ index 00000000..e1a7b4e0
 +void
 +pkcs11_uri_cleanup(struct pkcs11_uri *pkcs11)
 +{
++	if (pkcs11 == NULL) {
++		return;
++	}
++
 +	free(pkcs11->id);
 +	free(pkcs11->module_path);
 +	free(pkcs11->token);