Storage sometimes return null

Ionic Framework ionic-v3
1

I’m building an app in multiple languages
I’m using SQL Storage lite for keeping the chosen language
but sometimes the storage returns null

<ion-item class="settings-items" no-border ion-item>
      <ion-icon class="img-view" item-start name="ios-globe">
      </ion-icon>
      <ion-label [ngClass]="(this.Platform.isRTL ) ? 'settings-textAr': 'settings-text' ">{{'LANG' | translate}}</ion-label>
      <ion-select mode="ios" [(ngModel)]="lang" item-end (ionChange)="switchLanguage()">
        <ion-option class="options" value="en" [selected]="lang === english">
          English
        </ion-option>
        <ion-option class="options" value="ar" [selected]="lang === arabic">
          العربية
        </ion-option>
      </ion-select>
    </ion-item>

select lang

  switchLanguage() {
    if (this.lang === 'en') {

      this.translate.use(this.lang)
      this.Platform.setDir('ltr', true)
      this.storage.set('DocLang' , JSON.stringify(this.lang))
    } else {

      this.Platform.setDir('rtl', true)
      this.translate.use(this.lang);
      this.storage.set('DocLang' , JSON.stringify(this.lang))

    }

getting the language and setting it with the direction

this.Storage.get('DocLang').then((val) => {
          this.lang = JSON.parse(val)

          console.log(this.lang)
          if (this.lang === 'en') {
            this.TranslateService.use('en');
            this.platform.setDir('ltr', true);

          } else if(this.lang === 'ar'){
            this.TranslateService.use('ar');
            this.platform.setDir('rtl', true);

          }
      });
2

See this post.