ionic 4 google-maps 5测试版"TypeError:无法读取null的属性'BaseClass‘“

npm install @ionic-native/google-maps@5

import { GoogleMaps } from '@ionic-native/google-maps';

@NgModule({
  ...
  providers: [
    ...
    GoogleMaps
    ...
  ]
  ...
})
export class AppModule { }

import { GoogleMaps, GoogleMap, GoogleMapsEvent } from '@ionic-native/google-maps';

@Component({
  selector: 'app-map',
  templateUrl: 'map.page.html',
  styleUrls: ['map.page.scss'],
})
export class MapPage implements OnInit {

  map: GoogleMap;

  constructor(private googleMaps: GoogleMaps) { }

  ngOnInit() {
    this.loadMap();
  }

  loadMap() {
    this.map = this.googleMaps.create('map_canvas');
    this.map.one(GoogleMapsEvent.MAP_READY).then(() => {
      console.log('Map is ready!');
    });
  }

}