[TIMOB-2583] Android: Webview evalJS causes a never-released semaphore lock (and thread lockup) if JS code contains error

To reproduce, here is some code for a window:

var win = Ti.UI.currentWindow;
var wv = Ti.UI.createWebView({url: 'http://www.google.com'});
wv.addEventListener('load', function(e) {
    wv.evalJS('Mickey'); // ReferenceError in browser JS
});
win.add(wv);

In the fail-case, that should lock up your application pretty good!