Allow only http and https to open a new window

src/browser/index.jsx

@@ -272,6 +272,9 @@ var MattermostView = React.createClass({
     webview.addEventListener('new-window', function(e) {
       var currentURL = url.parse(webview.getURL());
       var destURL = url.parse(e.url);
+      if (destURL.protocol !== 'http:' && destURL.protocol !== 'https:'){
+        return;
+      }
       if (currentURL.host === destURL.host) {
         // New window should disable nodeIntergration.
         window.open(e.url, 'Mattermost', 'nodeIntegration=no');