[FIX] web: avoid crash when the Home client action is called without action param

E.g. this could happen when the HistoryBack client action
was unable to restore the previous breadcrumbs item, and
used the Home action as fallback. Could be reproduce by
performing a successful import from an action without
menu and context, such as what you get after refreshing
your browser.

bzr revid: odo@openerp.com-20140107161154-430y7hlf9mvtfyfe

addons/web/static/src/js/chrome.js

@@ -819,7 +819,7 @@ instance.web.client_actions.add("history_back", "instance.web.HistoryBack");
  */
 instance.web.Home = function(parent, action) {
     var url = '/' + (window.location.search || '');
-    instance.web.redirect(url, action.params && action.params.wait);
+    instance.web.redirect(url, action && action.params && action.params.wait);
 };
 instance.web.client_actions.add("home", "instance.web.Home");