Index: /CKEditor/trunk/_source/plugins/dialog/plugin.js
===================================================================
--- /CKEditor/trunk/_source/plugins/dialog/plugin.js	(revision 6954)
+++ /CKEditor/trunk/_source/plugins/dialog/plugin.js	(revision 6955)
@@ -110,5 +110,5 @@
 	{
 		var input = this.getInputElement();
-		input.removeAttribute( 'aria-invalid' );
+		input && input.removeAttribute( 'aria-invalid' );
 	}