Tolerate null oid pointer in gss_release_oid()

Under some circumstances, gss_inquire_name() can call
gss_release_oid() with a null oid pointer, which currently causes a
null dereference.  The least invasive fix is for gss_release_oid() to
check for the invalid null pointer and return an error, like other
GSS-API functions do.

(cherry picked from commit 4676e82)

ticket: 8201
version_fixed: 1.13.3
status: resolved

src/lib/gssapi/mechglue/g_initialize.c

@@ -168,7 +168,7 @@ gss_OID *oid;
 	OM_uint32 major;
 	gss_mech_info aMech;
 
-	if (minor_status == NULL)
+	if (minor_status == NULL || oid == NULL)
 		return (GSS_S_CALL_INACCESSIBLE_WRITE);
 
 	*minor_status = gssint_mechglue_initialize_library();