Fix function signature -> warning about signature mismatch solved

includes/rules-shipping-method.php

@@ -142,7 +142,7 @@ class Shipping_by_Rules extends WC_Shipping_Method {
 	 * @param mixed $package
 	 * @return void
 	 */
-	public function calculate_shipping( $package ) {
+	public function calculate_shipping( $package = array()) {
 		$methods = $this->helper->get_rule_shipping_methods();
 		foreach ($methods as $method) {