Use this
window.parent.CallParent();
instead of
window.opener.CallParent();
window.parent
holds a reference to the parent of the current window or subframe.
If a window does not have a parent, its parent
property is a reference to itself.
When a window is loaded in an <iframe>
, <object>
, or <frame>
, its parent is the window with the element embedding the window.
Reference: https://developer.mozilla.org/en-US/docs/Web/API/Window/parent