Trying to get property 'notParentItems' of non-object

(1/1) ErrorException

Trying to get property 'notParentItems' of non-object

in CollectionController.php line 46
at HandleExceptions->handleError()in CollectionController.php line 46
at CollectionController->setItems()in CollectionController.php line 19
at CollectionController->__construct()
at ReflectionClass->newInstanceArgs()in Container.php line 843
at Container->build()in Container.php line 681
at Container->resolve()in Application.php line 785
at Application->resolve()in Container.php line 629
at Container->make()in Application.php line 770
at Application->make()in Route.php line 233
at Route->getController()in Route.php line 833
at Route->controllerMiddleware()in Route.php line 794
at Route->gatherMiddleware()in Router.php line 694
at Router->gatherRouteMiddleware()in Router.php line 674
at Router->runRouteWithinStack()in Router.php line 658
at Router->runRoute()in Router.php line 624
at Router->dispatchToRoute()in Router.php line 613
at Router->dispatch()in Kernel.php line 170
at Kernel->Illuminate\Foundation\Http\{closure}()in Pipeline.php line 130
at Pipeline->Illuminate\Pipeline\{closure}()in TransformsRequest.php line 21
at TransformsRequest->handle()in Pipeline.php line 171
at Pipeline->Illuminate\Pipeline\{closure}()in TransformsRequest.php line 21
at TransformsRequest->handle()in Pipeline.php line 171
at Pipeline->Illuminate\Pipeline\{closure}()in ValidatePostSize.php line 27
at ValidatePostSize->handle()in Pipeline.php line 171
at Pipeline->Illuminate\Pipeline\{closure}()in CheckForMaintenanceMode.php line 63
at CheckForMaintenanceMode->handle()in Pipeline.php line 171
at Pipeline->Illuminate\Pipeline\{closure}()in TrustProxies.php line 57
at TrustProxies->handle()in Pipeline.php line 171
at Pipeline->Illuminate\Pipeline\{closure}()in Pipeline.php line 105
at Pipeline->then()in Kernel.php line 145
at Kernel->sendRequestThroughRouter()in Kernel.php line 110
at Kernel->handle()in index.php line 55