ERROR TypeError: Cannot read property 'subscribe' of undefined

I have use ng2-smart-table with datepicker. it returns Cannot read property 'subscribe' of undefined. use component: DatepickerComponent

 import { DatepickerComponent } from '../forms/datepicker/datepicker.component';
    export class LicenceDeviceComponent implements OnInit {
      settings = {
        columns: {
          licence_expiry_date: {
            title: 'Licence Expiry Date',
            type: 'string',
            editor: {
              type: 'custom',
              component: DatepickerComponent,
            },
            filter: {
              type: 'custom',
              component: DatepickerComponent,
            },
          },
        },
      };
    }

This my Datepicker component forms/datepicker/datepicker.component

import { Component } from '@angular/core';
import { NbDateService } from '@nebular/theme';

@Component({
  selector: 'ngx-datepicker',
  templateUrl: 'datepicker.component.html',
  styleUrls: ['datepicker.component.scss'],
})

export class DatepickerComponent {
  constructor(protected dateService: NbDateService<Date>) {}
}

forms/datepicker/datepicker.component.html

<input nbInput placeholder="Select Expiry Date" [nbDatepicker]="formpicker" id="expiry_date" #licence_expiry_date>
<nb-datepicker #formpicker format="yyyy-MM-dd"></nb-datepicker>