Call to a member function questions() on null

(1/1) Error

Call to a member function questions() on null

in FrontQuestionController.php line 464
at FrontQuestionController->filterByTagOrCategory('category', '%D9%BE%D8%B1%D8%A7%DB%8C%D8%B3-%D8%A7%DA%A9%D8%B4%D9%86-%D8%A8%D9%87-%D8%B3%D8%A8%DA%A9-%D9%81%D9%88%D9%84%D8%B1')
at call_user_func_array(array(object(FrontQuestionController), 'filterByTagOrCategory'), array('type' => 'category', 'tag' => '%D9%BE%D8%B1%D8%A7%DB%8C%D8%B3-%D8%A7%DA%A9%D8%B4%D9%86-%D8%A8%D9%87-%D8%B3%D8%A8%DA%A9-%D9%81%D9%88%D9%84%D8%B1'))in Controller.php line 54
at Controller->callAction('filterByTagOrCategory', array('type' => 'category', 'tag' => '%D9%BE%D8%B1%D8%A7%DB%8C%D8%B3-%D8%A7%DA%A9%D8%B4%D9%86-%D8%A8%D9%87-%D8%B3%D8%A8%DA%A9-%D9%81%D9%88%D9%84%D8%B1'))in ControllerDispatcher.php line 45
at ControllerDispatcher->dispatch(object(Route), object(FrontQuestionController), 'filterByTagOrCategory')in Route.php line 219
at Route->runController()in Route.php line 176
at Route->run()in Router.php line 680
at Router->Illuminate\Routing\{closure}(object(Request))in Pipeline.php line 30
at Pipeline->Illuminate\Routing\{closure}(object(Request))in VerifyCsrfToken.php line 75
at VerifyCsrfToken->handle(object(Request), object(Closure))in Pipeline.php line 163
at Pipeline->Illuminate\Pipeline\{closure}(object(Request))in Pipeline.php line 53
at Pipeline->Illuminate\Routing\{closure}(object(Request))in SubstituteBindings.php line 41
at SubstituteBindings->handle(object(Request), object(Closure))in Pipeline.php line 163
at Pipeline->Illuminate\Pipeline\{closure}(object(Request))in Pipeline.php line 53
at Pipeline->Illuminate\Routing\{closure}(object(Request))in ShareErrorsFromSession.php line 49
at ShareErrorsFromSession->handle(object(Request), object(Closure))in Pipeline.php line 163
at Pipeline->Illuminate\Pipeline\{closure}(object(Request))in Pipeline.php line 53
at Pipeline->Illuminate\Routing\{closure}(object(Request))in AddQueuedCookiesToResponse.php line 37
at AddQueuedCookiesToResponse->handle(object(Request), object(Closure))in Pipeline.php line 163
at Pipeline->Illuminate\Pipeline\{closure}(object(Request))in Pipeline.php line 53
at Pipeline->Illuminate\Routing\{closure}(object(Request))in EncryptCookies.php line 66
at EncryptCookies->handle(object(Request), object(Closure))in Pipeline.php line 163
at Pipeline->Illuminate\Pipeline\{closure}(object(Request))in Pipeline.php line 53
at Pipeline->Illuminate\Routing\{closure}(object(Request))in Pipeline.php line 104
at Pipeline->then(object(Closure))in Router.php line 682
at Router->runRouteWithinStack(object(Route), object(Request))in Router.php line 657
at Router->runRoute(object(Request), object(Route))in Router.php line 623
at Router->dispatchToRoute(object(Request))in Router.php line 612
at Router->dispatch(object(Request))in Kernel.php line 176
at Kernel->Illuminate\Foundation\Http\{closure}(object(Request))in Pipeline.php line 30
at Pipeline->Illuminate\Routing\{closure}(object(Request))in StartSession.php line 56
at StartSession->handle(object(Request), object(Closure))in Pipeline.php line 163
at Pipeline->Illuminate\Pipeline\{closure}(object(Request))in Pipeline.php line 53
at Pipeline->Illuminate\Routing\{closure}(object(Request))in CheckForMaintenanceMode.php line 62
at CheckForMaintenanceMode->handle(object(Request), object(Closure))in Pipeline.php line 163
at Pipeline->Illuminate\Pipeline\{closure}(object(Request))in Pipeline.php line 53
at Pipeline->Illuminate\Routing\{closure}(object(Request))in Pipeline.php line 104
at Pipeline->then(object(Closure))in Kernel.php line 151
at Kernel->sendRequestThroughRouter(object(Request))in Kernel.php line 116
at Kernel->handle(object(Request))in index.php line 53