Index: t3lib/js/extjs/ux/Ext.ux.FitToParent.js
===================================================================
--- t3lib/js/extjs/ux/Ext.ux.FitToParent.js	(revision 10282)
+++ t3lib/js/extjs/ux/Ext.ux.FitToParent.js	(revision )
@@ -24,7 +24,8 @@
 
 	fitSizeToParent : function() {
 			// Uses the dimension of the current viewport, but removes the document header
-		var documentHeaderHeight = top.TYPO3.Backend.Topbar.getHeight();
+			// initial is the heigt of the TYPO3 Topbar which i 42. If Topbar is not rendered, set the height as default
+		var documentHeaderHeight = 42 || top.TYPO3.Backend.Topbar.getHeight();
 		var documentHeader = Ext.get('typo3-docheader');
 
 		if (Ext.isObject(documentHeader)) {