Update swing-stack.component.ts

Fixed the void return.

I think it's easier to get the card this way, instead of comparing elements.

Author: fobaz

src/app/modules/ionic-swing/components/swing-stack.component.ts

@@ -53,7 +53,7 @@ export class SwingStackComponent implements AfterContentInit {
     addCard(card: SwingCardComponent) {
         this.cards.push(card);
         if (this.stack) {
-            this.stack.createCard(card.getNativeElement());
+            return this.stack.createCard(card.getNativeElement());
         }
     }