MAGETWO-57805: [mainline] It is possible to delete self admin account or role

Author: Yaroslav Onischenko

app/code/Magento/User/Controller/Adminhtml/User/Delete.php

@@ -14,8 +14,8 @@ class Delete extends \Magento\User\Controller\Adminhtml\User
     public function execute()
     {
         $currentUser = $this->_objectManager->get(\Magento\Backend\Model\Auth\Session::class)->getUser();
-
-        if ($userId = (int)$this->getRequest()->getPost('user_id')) {
+        $userId = (int)$this->getRequest()->getPost('user_id');
+        if ($userId) {
             if ($currentUser->getId() == $userId) {
                 $this->messageManager->addError(__('You cannot delete your own account.'));
                 $this->_redirect('adminhtml/*/edit', ['user_id' => $userId]);