(legacy) xmlrpc sync fix for https://github.com/opnsense/core/issues/254

When the target has no entries at all, it doesn't know how to merge.

src/etc/inc/xmlrpc/legacy.inc

@@ -116,6 +116,9 @@ function array_merge_recursive_unique($array0, $array1) {
 						$result[$key] = call_user_func_array(__FUNCTION__, $args);
 					} else {
 						foreach($value as $vkey => $vval) {
+							if (!isset($result[$key]) || !is_array($result[$key])) {
+								$result[$key] = array();
+							}
 							$result[$key][$vkey] = $vval;
 						}
 					}