Skip empty implements list

src/app/type-details.component.html

 <div *ngIf="type">
   <h2>{{type.kind}} {{type.name}}</h2>
   <p *ngIf="type.superclass">extends <type-ref [type]="type.superclass"></type-ref>
-  <ng-container *ngIf="type.superinterfaces">implements <ng-container *ngFor="let iface of type.superinterfaces; let isLast = last"><type-ref [type]="iface"></type-ref><div *ngIf="!isLast" class="sep">, </div></ng-container></ng-container>
+  <ng-container *ngIf="type.superinterfaces.length > 0">implements <ng-container *ngFor="let iface of type.superinterfaces; let isLast = last"><type-ref [type]="iface"></type-ref><div *ngIf="!isLast" class="sep">, </div></ng-container></ng-container>
   </p>
   <p>
   <ng-container *ngIf="type.subtypes">Direct subtypes: <ng-container *ngFor="let subtype of type.subtypes; let isLast = last"><type-ref [type]="subtype"></type-ref><div *ngIf="!isLast" class="sep">, </div></ng-container></ng-container>