コメントありがとうございます。デバッグモードが分からず、すぐに返信できませんでした。デバッグモードでのエラーメッセージは以下の通りでした。私にはよく分からないのですが、解決のアドバイス、よろしくお願いします。

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in AbstractQuery.php line 657
at AbstractQuery->getSingleResult() in PointStatusRepository.php line 99
at PointStatusRepository->isFixedStatus(object(Order)) in AdminOrder.php line 87
at AdminOrder->createForm(object(EventArgs)) in PointEvent.php line 112
at PointEvent->onAdminOrderEditIndexInitialize(object(EventArgs), 'admin.order.edit.index.initialize', object(EventDispatcher))
at call_user_func(array(object(PointEvent), 'onAdminOrderEditIndexInitialize'), object(EventArgs), 'admin.order.edit.index.initialize', object(EventDispatcher)) in EventDispatcher.php line 161
at EventDispatcher->doDispatch(array(array(object(PointEvent), 'onAdminOrderEditIndexInitialize')), 'admin.order.edit.index.initialize', object(EventArgs)) in EventDispatcher.php line 46
at EventDispatcher->dispatch('admin.order.edit.index.initialize', object(EventArgs)) in EditController.php line 107
at EditController->index(object(Application), object(Request), '152')
at call_user_func_array(array(object(EditController), 'index'), array(object(Application), object(Request), '152')) in HttpKernel.php line 144
at HttpKernel->handleRaw(object(Request), '1') in HttpKernel.php line 64
at HttpKernel->handle(object(Request), '1', true) in Application.php line 586
at Application->handle(object(Request)) in Application.php line 563
at Application->run() in index_dev.php line 108