title: in-app billing mHelper.dispose() error
body: <p>I'm tryng to implement in-app-billing.</p>
  
  <p>When i follow the tutorial and add the lines bellow to my app:</p>
  
  <pre><code> public void onDestroy() {
          super.onDestroy();
          if (mHelper != null) mHelper.dispose();
          mHelper = null;
  </code></pre>
  
  <p>i receive the following error:</p>
  
  <pre><code>Error:(216, 45) error: unreported exception IabAsyncInProgressException; must be caught or declared to be thrown
  </code></pre>
  
  <p>The strange thing is when i replace <code>mHelper.dispose()</code> for <code>mHelper.disposeWhenFinished()</code> it works.</p>
  
  <p>I'm worried cause the same error appears again in </p>
  
  <pre><code>mHelper.launchPurchaseFlow(this,ITEM_SKU,1001,mPurchaseFinishedListener,hpacote);
  </code></pre>
  
  <p>Thanks</p>