title: Can't have 2 UI instances using google scripts
body: <p>I have a google spreadsheet in which I've build a script (Web App) that displays a control panel with buttons using uiapp. </p>
  
  <pre><code>var app = UiApp.createApplication().setHeight(160).setWidth(95);
  </code></pre>
  
  <p>However, when I open a Browser message box, or a htmlservice, it closes the control-panel.</p>
  
  <pre><code>Browser.msgBox('Backup Completed');
  var t = HtmlService.createTemplateFromFile('BuildNotes').evaluate().setHeight(800).setWidth(1000).setTitle("Preview");
  </code></pre>
  
  <p>Can i only have one GUI up? Is there possibly a way to capture when a GUI is closed, so i can restart the control panel?</p>