Backport (CMS7-7165): Regression: Can't open document in editor

To reproduce:

• Go to the Browse perspective
• Browse to a document, and click it
  Expected result: The document opens in the document editor
  Actual result: The document doesn't open. A javascript error occurs:

Uncaught ReferenceError: InstallTrigger is not defined (localhost/:8)
window.XinhaTools (localhost/:8)
(anonymous function) (localhost/:228)
Wicket.Head.addElement (wicket-ajax.js:1809)
Wicket.Head.addJavascript (wicket-ajax.js:1865)
onLoad (wicket-ajax.js:1745)
Wicket.Ajax.Request.stateChangeCallback (wicket-ajax.js:1055)