OverlayPanel show method not working

[andyg3]

I'm submitting a ... (check one with "x")

[X ] bug report 

Plunkr Case (Bug Reports)
https://stackblitz.com/edit/overlaypanel-noshow

Current behavior

Calling show() method on OverlayPanel does nothing.

Expected behavior

Show method should make the panel appear.

Minimal reproduction of the problem with instructions
https://stackblitz.com/edit/overlaypanel-noshow

What is the motivation / use case for changing the behavior?

Please tell us about your environment:

• Angular version: 6.1.3

• PrimeNG version: 6.1.3

• Browser: [all | Chrome XX | Firefox XX | IE XX | Safari XX | Mobile Chrome XX | Android X.X Web Browser | iOS XX Safari | iOS XX UIWebView | iOS XX WKWebView ]

Tested in Chrome

• Language: [all | TypeScript X.X | ES6/7 | ES5]

Note: It works fine in 6.1.2