Application error connection to server was unsuccessfull

Hi i was working with ionic2 app, App worked well, today i add this plugin “ionic plugin add cordova-crosswalk-webview” after this i try to run the same android device but my device gives an alert that application error "connection to the server was unsuccessful. (file:///android-assert/www/index.html) "
i browsed and got some clues like adding this to config.xml

no use still the problem is presisting