fix(phpstan): code improvements and resolve warnings

Reviewed code and made several improvements which provide better error handling, code quality, and resolved warnings. The changes include:

• Syntax modifications for better readability,
• Ensured variable type checks before using methods,
• Resolved warning instances in phpstan,
• Adapted code to comply with modern PHP nullable type indicator.

Alongside, made version update in phive/phars.xml. Also, unnecessary comments or instances are removed for a cleaner code.

Related: #16 (closed)

bin/frontend/controls/CouponCodeInput.js

@@ -23,7 +23,7 @@ define('package/quiqqer/coupons/bin/frontend/controls/CouponCodeInput', [
 ], function(QUI, QUIControl, QUILoader, Sessions, CouponCodes, QUIAjax, QUILocale, Mustache, template) {
     'use strict';
 
-    var lg = 'quiqqer/coupons';
+    const lg = 'quiqqer/coupons';
 
     return new Class({
 
@@ -50,8 +50,8 @@ define('package/quiqqer/coupons/bin/frontend/controls/CouponCodeInput', [
          * Event: onInject
          */
         $onInject: function() {
-            var self = this;
-            var lgPrefix = 'controls.frontend.CouponCodeInput.template.';
+            const self = this;
+            const lgPrefix = 'controls.frontend.CouponCodeInput.template.';
 
             this.$Elm.addClass('quiqqer-coupons-field');
 
@@ -81,7 +81,7 @@ define('package/quiqqer/coupons/bin/frontend/controls/CouponCodeInput', [
             });
 
             if (this.isInOrder()) {
-                var OrderProcess = this.getOrderProcess();
+                const OrderProcess = this.getOrderProcess();
 
                 new Promise(function(resolve) {
                     if (!OrderProcess.isLoaded()) {
@@ -118,8 +118,8 @@ define('package/quiqqer/coupons/bin/frontend/controls/CouponCodeInput', [
                 return;
             }
 
-            var self = this;
-            var code = this.$Input.value.trim();
+            const self = this;
+            const code = this.$Input.value.trim();
 
             if (code === '') {
                 this.$Input.focus();
@@ -192,7 +192,7 @@ define('package/quiqqer/coupons/bin/frontend/controls/CouponCodeInput', [
                 return;
             }
 
-            var OrderProcess = this.getOrderProcess();
+            const OrderProcess = this.getOrderProcess();
 
             OrderProcess.Loader.show();
 
@@ -239,7 +239,7 @@ define('package/quiqqer/coupons/bin/frontend/controls/CouponCodeInput', [
          * @return {boolean}
          */
         isInOrder: function() {
-            var OrderProcessNode = this.getElm().getParent(
+            const OrderProcessNode = this.getElm().getParent(
                 '[data-qui="package/quiqqer/order/bin/frontend/controls/OrderProcess"]'
             );
 
@@ -252,7 +252,7 @@ define('package/quiqqer/coupons/bin/frontend/controls/CouponCodeInput', [
          * @return {Object}
          */
         getOrderProcess: function() {
-            var OrderProcessNode = this.getElm().getParent(
+            const OrderProcessNode = this.getElm().getParent(
                 '[data-qui="package/quiqqer/order/bin/frontend/controls/OrderProcess"]'
             );
 
@@ -269,10 +269,10 @@ define('package/quiqqer/coupons/bin/frontend/controls/CouponCodeInput', [
                 return Promise.resolve();
             }
 
-            var self = this;
+            const self = this;
 
             return new Promise(function(resolve) {
-                var OrderProcess = self.getOrderProcess();
+                const OrderProcess = self.getOrderProcess();
 
                 OrderProcess.Loader.show();
                 OrderProcess.getOrder().then(function(orderHash) {