Siebel IP17 Applet Weblayout editor is not Opening

In Siebel IP17 once you will open Weblayout editor to arrange controls on the template then you won't be able to see anything and if you look into the browser console, you will see below error:

Uncaught TypeError: this.GetUIWrapper(...).BuildPreview is not a function

 The issue is caused by the following setup: Customization added at JS level.
WebTools is the correspondent of Tools, and should, therefore, contain no customizations. This includes JS files. 

In order to fix this use below parameters:

Manifest Safe Load : TRUE
Enable Safe Boot : TRUE