Modal slides are not displayed in ionic4

I’m migrating source code from ionic3 to ionic4.

The following slide page is not displayed in ionic4.

How do I fix it?

I hope you would tell me.

app.component.ts (The calling page)

async error => {

const walkthroughModal = await this.modalCtrl.create({component: WalkthroughPage, componentProps:{prev_page: 'login'} });
    await walkthroughModal.present();

    	selector: 'page-walkthrough',
    	templateUrl: '',
    	styleUrls: [''],
    	providers: [CustomNativeStorage]
    export class WalkthroughPage {
	@ViewChild('slides', {static: false}) slides: IonSlides;

<ion-slides pager="true">
	<ion-slide *ngFor="let slide of walkthroughSlides" [style.background-image]="slide.img">
		<div class="walkthrough-content-card">
			<div class="text-container">
				<div class="walkthrough-title">
					{{ slide.title }}
				<div class="walkthough-text">
					{{ slide.text }}
			<div class="button-container">
				<ion-button class="button_continue" color="bright" (click)="slideNext()">