Updated PHPStan to 2.2.6 and fixed the new unnecessary null-coalesce errors

app/code/core/Mage/Admin/Model/Session.php

@@ -162,6 +162,8 @@ public function login(#[\SensitiveParameter] string $username, #[\SensitiveParam
             return null;
         }
 
+        $user = null;
+
         try {
             /** @var Mage_Admin_Model_User $user */
             $user = $this->_factory->getModel('admin/user');
@@ -200,7 +202,7 @@ public function login(#[\SensitiveParameter] string $username, #[\SensitiveParam
             $this->_loginFailed($e, $request, $username, $message);
         }
 
-        return $user ?? null;
+        return $user;
     }
 
     /**

app/code/core/Mage/Adminhtml/Block/Widget/Grid/Column/Renderer/Datetime.php

@@ -40,7 +40,7 @@ public function render(\Maho\DataObject $row)
         if ($data = $this->_getValue($row)) {
             try {
                 $useTimezone = $this->getColumn()->getUseTimezone() ?? true;
-                $locale = $this->getColumn()->getLocale() ?? null;
+                $locale = $this->getColumn()->getLocale();
 
                 $dateObj = $useTimezone
                     ? Mage::app()->getLocale()->utcToStore(null, $data)

app/code/core/Mage/Payment/Model/Restriction/Rule/Condition/Product.php

@@ -38,7 +38,7 @@ public function __construct()
      */
     public function getRule()
     {
-        return $this->_rule ?? null;
+        return $this->_rule;
     }
 
     /**

app/code/core/Mage/Sales/Helper/Guest.php

@@ -149,7 +149,7 @@ protected function _loadOrderByCookie($cookie = null)
     {
         if (!is_null($cookie)) {
             $cookieData = explode(':', base64_decode($cookie));
-            $protectCode = $cookieData[0] ?? null;
+            $protectCode = $cookieData[0];
             $incrementId = $cookieData[1] ?? null;
 
             if (!empty($protectCode) && !empty($incrementId)) {

app/code/core/Maho/Ai/Helper/Data.php

@@ -130,7 +130,7 @@ public function submitTask(array $data): int
         // path in invoke(). Without this the async queue would be a bypass
         // around the same guard that protects synchronous calls.
         foreach ($data['messages'] ?? [] as $msg) {
-            if (($msg['role'] ?? null) === 'user') {
+            if (($msg['role'] ?? '') === 'user') {
                 $validation = $this->getInputValidator()->validate((string) ($msg['content'] ?? ''));
                 if (!$validation['safe']) {
                     throw new Mage_Core_Exception('AI request rejected: ' . $validation['reason']);