failed in _destroyOverlay when I destroy a modal dialog thau was never opened.

[JMGrange]

I create a modal dialog. If I show this dialog the destroy works fine. If I call the destroy dialog function without showing at least one time this dialog, the _destroyOverlay function failed beacause overlay is null. I solve the problem by testing the overlayInstances value.

if ( $.ui.dialog.overlayInstances > 0 ) {

$.ui.dialog.overlayInstances--; if ( !$.ui.dialog.overlayInstances ) {

this._off( this.document, "focusin" );

} this.overlay.remove();

}

[Scott González]

Duplicate of #9004.