[FIX] core.Popup: Removal of the Old DOM-Ref
[FIX] core.Popup: Removal of the Old DOM-Ref

- when the popup is closed somehow the application did so much weird
stuff that the manipulated DOM-ref of the popup remains on screen. Now
the second removal always hides the DOM-ref if there is a DOM-ref left.

BCP: 1570011268
Change-Id: I8c584b3e8d7a367b765c70f5181911a3e3255f28

nzamani/openui5,SQCLabs/openui5,cschuff/openui5,olirogers/openui5,SAP/openui5,nzamani/openui5,olirogers/openui5,nzamani/openui5,SAP/openui5,SQCLabs/openui5,cschuff/openui5,olirogers/openui5,SAP/openui5,cschuff/openui5,SAP/openui5,SQCLabs/openui5