Steps to Reproduce

1. Open a url with launch()
2. attempt to close with closeWebView()
3. nothing happens

Problem

In UrlLauncherPlugin.m around line 133, a completion handler is set that resets _currentSession to nil, however completion of presentViewController is called as completion of showing the viewcontroller, and not at the end of the web browsing.

As such, _currentSession is reset to nil almost immediately, and closeWebView() will do nothing.

I am guessing safariViewControllerDidFinish in the delegate should instead be used.