maybe works

src/app/ygopro/ygopro.component.html

@@ -33,18 +33,6 @@
           <option *ngFor="let deck of group.value" [value]="group.key + '/' + deck">{{deck}}</option>
         </optgroup>
       </ng-container>
-
-
-<!--      <option *ngFor="let deck of group[1]" [value]="group[0] + '/' + deck">{{deck}}</option>-->
-<!--      -->
-<!--      <ng-container *ngFor="let group of deck_grouped | keyvalue">-->
-<!--        <ng-container *ngIf="group[0] == '.'; else #x">-->
-
-<!--        </ng-container>-->
-<!--        <ng-template #elseBlock>Content to render when condition is false.</ng-template>-->
-<!--        <optgroup [label]="group[0]"></optgroup>-->
-<!--        <option *ngFor="let deck of group[1]" [value]="group[0] + '/' + deck">{{deck}}</option>-->
-<!--      </ng-container>-->
     </select>
     <span class="input-group-btn">
         <button id="edit_deck_button" i18n [disabled]="!appsService.allReady(app)" class="btn btn-secondary btn-sm" (click)="edit_deck(current_deck)">编辑</button>