Merge pull request 'WP PLUGIN バグ修正（カスタムフィールドの値がない場合）' (#8) from バグ修正_カスタムフィールドの値がない場合 into master

Reviewed-on: https://develop.n-k-y.net/repo/WP_PLUGIN/POST_ORDER_BY_ARCHIVE/pulls/8

util/apop-order-setting.php

@@ -192,6 +192,9 @@ if ( ! trait_exists( 'APOP_ORDER_SETTING' ) ) {
 		}
 
 		private static function set_custom_field_orderby( $apop_order_param ): array {
+			if ( ! $apop_order_param ) {
+				return array();
+			}
 			$sort_param = array( 1 => 'ASC', 2 => 'DESC' );
 			$meta_query = null;
 			$orderby    = null;