Index: /CKEditor/tests/js/unit.js
===================================================================
--- /CKEditor/tests/js/unit.js	(revision 4438)
+++ /CKEditor/tests/js/unit.js	(revision 4439)
@@ -92,5 +92,5 @@
 		this.config = null;
 		// The initial editor data loaded.
-		this.startupData = null;
+		this.startupData = '';
 
 		CKEDITOR.test.suites.editorTestSuite.superclass.constructor.call( this, template );