title: Ionic 2 ion-item-sliding error when updating object
body: <p>i'm trying to use the ion-item-sliding of a ion-list with this code :</p>
  
  <pre><code>&lt;ion-list&gt;
  &lt;ion-item-sliding *ngFor="let device of devices" class="item-sliding-joueur-balise"&gt;
      &lt;ion-item class="item-joueur-balise" *ngIf="device.player"&gt;
      &lt;ion-avatar item-left&gt;&lt;img left="" src={{device.player.urlImage}}/&gt;&lt;/ion-avatar&gt;
      &lt;ion-label&gt;{{device.player.name}}&lt;/ion-label&gt;
      &lt;ion-label right&gt;Balise {{device.id}}&lt;/ion-label&gt;
  &lt;/ion-item&gt;
  &lt;ion-item-options side="right"&gt;
      &lt;button ion-button class="button-edit-balise" (click)="handleEditBalise(device)"&gt;
      &lt;ion-icon class="icon-action" name="md-create"&gt;&lt;/ion-icon&gt;
      &lt;label class="label-action"&gt;Balise&lt;/label&gt;
      &lt;/button&gt;
      &lt;button ion-button color="danger" style="width:80px" (click)="deleteDevice(device)"&gt;
      &lt;ion-icon class="icon-action-size" name="trash"&gt;&lt;/ion-icon&gt;
      &lt;label class="label-action"&gt;Supprimer&lt;/label&gt;
      &lt;/button&gt;
  &lt;/ion-item-options&gt;
  &lt;/ion-item-sliding&gt;
  </code></pre>
  
  <p></p>
  
  <p>But when I click on the delete button that executes the deleteDevice(device)
  , I get the following error :</p>
  
  <pre><code>Uncaught TypeError: Cannot read property 'setElementStyle' of undefined
      at ItemSliding._setOpenAmount (item-sliding.js:396)
      at ItemSliding.close (item-sliding.js:477)
      at ItemSlidingGesture.closeOpened (item-sliding-gesture.js:104)
      at ItemSlidingGesture.canStart (item-sliding-gesture.js:50)
      at ItemSlidingGesture.PanGesture.pointerDown (drag-gesture.js:79)
      at PointerEvents.handleTouchStart (pointer-events.js:43)
  </code></pre>
  
  <p>The deleteDevice function is :</p>
  
  <pre><code> deleteDevice(device: Device): void {
      device.player= null;
      }
  </code></pre>
  
  <p>I seems that when I try to modify the device element of the list i get this error but i don't know how to solve it and why is it happening.</p>
  
  <p>Any ideas please ? (i don't want to use the splice function on devices but juste set the player of the device to null)</p>
  
  <p>Thank you.</p>