title: Error displaying modal using BsModalService
body: <p>I'm trying to display a modal using the service and get the following error. I can successfully call the service from a button but get this error when calling from an error handler.</p>
  
  <pre><code>TypeError: Cannot read property 'attachView' of undefined
  at ComponentLoader.webpackJsonp.../../../../ngx-bootstrap/component-loader/component-loader.class.js.ComponentLoader.show (vendor.bundle.js:19572)
  at BsModalService.webpackJsonp.../../../../ngx-bootstrap/modal/bs-modal.service.js.BsModalService._showBackdrop (vendor.bundle.js:21508)
  at BsModalService.webpackJsonp.../../../../ngx-bootstrap/modal/bs-modal.service.js.BsModalService.show
  </code></pre>
  
  <p>Here is my calling code:</p>
  
  <pre><code>import { Injectable } from "@angular/core";
  import { BsModalService, BsModalRef  } from "ngx-bootstrap/modal";
  import { MessageBoxComponent } from "../message-box/message-box.component";
  
  @Injectable()
  export class NotificationService {
    private modalRef: BsModalRef;
  
    constructor(private modalService: BsModalService) {}
  
      showModal(type: string, title: string, message: any) {  
        this.modalRef = this.modalService.show(MessageBoxComponent);
        this.modalRef.content.type = type;
        this.modalRef.content.title = title;
        this.modalRef.content.message = message.toString();
      }
  }
  </code></pre>
  
  <p>And the app module:</p>
  
  <pre><code>import { NgModule } from '@angular/core';
  import { ModalModule } from 'ngx-bootstrap/modal';
  
  import { MessageBoxComponent } from './modules/common/message-box/message-box.component';
  
  @NgModule({
    entryComponents: [MessageBoxComponent],
    imports: [ModalModule.forRoot()]
    //...etc
  })
  export class AppModule { }
  </code></pre>
  
  <p>Can anyone help me?</p>