Error: Call to a member function getStatusCode() on null in drupalchat_user_logout() (line 90 of modules\drupalchat\drupalchat.module).

I have installed and activated drupalchat-8.x-1.0-beta2 but it is giving me some errors while i try to click on logout link 'The website encountered an unexpected error. Please try again later.'
And when i enabled the error logs i found some below errors-
The website encountered an unexpected error. Please try again later.
Error: Call to a member function getStatusCode() on null in drupalchat_user_logout() (line 90 of modules\drupalchat\drupalchat.module).
drupalchat_user_logout(Object)
call_user_func_array('drupalchat_user_logout', Array) (Line: 402)
Drupal\Core\Extension\ModuleHandler->invokeAll('user_logout', Array) (Line: 1396)
user_logout() (Line: 281)
Drupal\user\Controller\UserController->logout()
call_user_func_array(Array, Array) (Line: 123)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (Line: 574)
Drupal\Core\Render\Renderer->executeInRenderContext(Object, Object) (Line: 124)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->wrapControllerExecutionInRenderContext(Array, Array) (Line: 97)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}()
call_user_func_array(Object, Array) (Line: 139)
Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object, 1) (Line: 62)
Symfony\Component\HttpKernel\HttpKernel->handle(Object, 1, 1) (Line: 57)
Drupal\Core\StackMiddleware\Session->handle(Object, 1, 1) (Line: 47)
Drupal\Core\StackMiddleware\KernelPreHandle->handle(Object, 1, 1) (Line: 99)
Drupal\page_cache\StackMiddleware\PageCache->pass(Object, 1, 1) (Line: 78)
Drupal\page_cache\StackMiddleware\PageCache->handle(Object, 1, 1) (Line: 47)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object, 1, 1) (Line: 50)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object, 1, 1) (Line: 23)
Stack\StackedHttpKernel->handle(Object, 1, 1) (Line: 652)
Drupal\Core\DrupalKernel->handle(Object) (Line: 19)

Please help me to sortout these issues.
Thanks in advance