Fatal error: Call to a member function getId() on boolean

This error is shown when I try to create an XML/Soap User, I click on add user and this error I got.

Fatal error: Call to a member function getId() on boolean in /var/www/vhosts/domain.com/httpdocs/app/code/core/Mage/Adminhtml/controllers/Api/UserController.php on line 74

this is my UserController.php

<?php

class Mage_Adminhtml_Api_UserController extends Mage_Adminhtml_Controller_Action
{
    public function indexAction()
    {
        $this->_title($this->__('System'))
            ->_title($this->__('Web Services'))
            ->_title($this->__('Users'));

        $this->_initAction()
            ->_addContent($this->getLayout()->createBlock('adminhtml/api_user'))
            ->renderLayout();
    }

    protected function _initAction()
    {
        $this->loadLayout()
            ->_setActiveMenu('system/services/users')
            ->_addBreadcrumb($this->__('Web Services'), $this->__('Web Services'))
            ->_addBreadcrumb($this->__('Permissions'), $this->__('Permissions'))
            ->_addBreadcrumb($this->__('Users'), $this->__('Users'));
        return $this;
    }

    public function newAction()
    {
        $this->_forward('edit');
    }

    public function editAction()
    {
        $this->_title($this->__('System'))
            ->_title($this->__('Web Services'))
            ->_title($this->__('Users'));

        $id = $this->getRequest()->getParam('user_id');
        $model = Mage::getModel('api/user');
        if ($id) {
            $model->load($id);
            if (!$model->getId()) {
                Mage::getSingleton('adminhtml/session')->addError($this->__('This user no longer exists.'));
                $this->_redirect('*/*/');
                return;
            }
        }
        $this->_title($model->getId() ? $model->getName() : $this->__('New User'));
        // Restore previously entered form data from session
        $data = Mage::getSingleton('adminhtml/session')->getUserData(true);
        if (!empty($data)) {
            $model->setData($data);
        }
        Mage::register('api_user', $model);
        $this->_initAction()
            ->_addBreadcrumb($id ? $this->__('Edit User') : $this->__('New User'),
                $id ? $this->__('Edit User') : $this->__('New User'))
            ->_addContent($this->getLayout()->createBlock('adminhtml/api_user_edit') -    >setData('action',
            $this->getUrl('*/api_user/save')))
                ->_addLeft($this->getLayout()->createBlock('adminhtml/api_user_edit_tabs'));
            $this->_addJs($this->getLayout()->createBlock('adminhtml/template')->setTemplate('api/user_roles_grid_js.phtml'));
            $this->renderLayout();
    }

    public function saveAction()
    {
        if ($data = $this->getRequest()->getPost()) {
            $id = $this->getRequest()->getPost('user_id', false);
            $model = Mage::getModel('api/user')->load($id);
            if (!$model->getId() && $id) {
                Mage::getSingleton('adminhtml/session')->addError($this->__('This user no longer exists.'));
                $this->_redirect('*/*/');
                return;
            }
            $model->setData($data);
            try {
                $model->save();
                if ($uRoles = $this->getRequest()->getParam('roles', false)) {
                    /*parse_str($uRoles, $uRoles);
                    $uRoles = array_keys($uRoles);*/
                    if (1 == sizeof($uRoles)) {
                        $model->setRoleIds($uRoles)
                            ->setRoleUserId($model->getUserId())
                            ->saveRelations();
                    } else {
                        if (sizeof($uRoles) > 1) {
                            //@FIXME: stupid fix of previous multi-roles logic.
                            //@TODO: make proper DB upgrade in the future revisions.
                            $rs = array();
                            $rs[0] = $uRoles[0];
                            $model->setRoleIds($rs)->setRoleUserId($model->getUserId()) -    >saveRelations();
                        }
                    }
                }
                Mage::getSingleton('adminhtml/session')->addSuccess($this->__('The user has been saved.'));
                Mage::getSingleton('adminhtml/session')->setUserData(false);
                $this->_redirect('*/*/edit', array('user_id' => $model->getUserId()));
                return;
            } catch (Exception $e) {
                Mage::getSingleton('adminhtml/session')->addError($e->getMessage());
                Mage::getSingleton('adminhtml/session')->setUserData($data);
                $this->_redirect('*/*/edit', array('user_id' => $model->getUserId()));
                return;
            }
        }
        $this->_redirect('*/*/');
    }

    public function deleteAction()
    {
        if ($id = $this->getRequest()->getParam('user_id')) {
            try {
                $model = Mage::getModel('api/user')->load($id);
                $model->delete();
                Mage::getSingleton('adminhtml/session')->addSuccess($this->__('The user has  been deleted.'));
                $this->_redirect('*/*/');
                return;
            } catch (Exception $e) {
                Mage::getSingleton('adminhtml/session')->addError($e->getMessage());
                $this->_redirect('*/*/edit', array('user_id' => $this->getRequest() -    >getParam('user_id')));
                return;
            }
        }
        Mage::getSingleton('adminhtml/session')->addError($this->__('Unable to find a user to delete.'));
        $this->_redirect('*/*/');
    }

    public function rolesGridAction()
    {
        $id = $this->getRequest()->getParam('user_id');
        $model = Mage::getModel('api/user');
        if ($id) {
            $model->load($id);
        }
        Mage::register('api_user', $model);
        $this->getResponse()->setBody($this->getLayout()->createBlock('adminhtml/api_user_edit_tab_roles')->toHtml());
    }

    public function roleGridAction()
    {
        $this->getResponse()
            ->setBody($this->getLayout()
                ->createBlock('adminhtml/api_user_grid')
                ->toHtml()
            );
    }

    protected function _isAllowed()
    {
        return Mage::getSingleton('admin/session')->isAllowed('system/api/users');
    }
}

and when I enabled the error reporting, I see this error from Log

mod_fcgid: stderr: PHP Fatal error: Call to a member function getId() on boolean in /var/www/vhosts/domain.com/httpdocs/app/code/core/Mage/Adminhtml/controllers/Api/UserController.php on line 74, referer: http://www.domain.com/index.php/admin/api_user/index/key/b2a855c2e5d82b8a3ba010f07f3883af/

and I saw this in my browser when I click on Add New user in SOAP/XML-RPC Users.

Fatal error: Call to a member function getId() on boolean in /var/www/vhosts/domain.com/httpdocs/app/code/core/Mage/Adminhtml/controllers/Api/UserController.php on line 74

Look into what the load() function returns in this context:

$model = Mage::getModel('api/user')->load($id);

Earlier in your script, you do a:

$model = Mage::getModel('api/user'); 

followed by a

$model->load($id);

I think where you have:

$model = Mage::getModel('api/user')->load($id);

You likewise need to do :

$model = Mage::getModel('api/user'); 
$model->load($id);

I can't say for sure without your providing more code, but I would guess that the load() function "loads" the corresponding $id's values into the object by setting certain class variables and returns True or False; it doesn't return the loaded object itself.