Fix history loop issue with /search

When an error occurs on the route /search, it defaults back to index
page.  But this error will happen with any bare (no params) search, so
you can get into a loop where the back button is constantly re-pushing
the index-page.
This now replaces the history entry on error, which should fix it.

src/js/apps/discovery/router.js

@@ -29,6 +29,8 @@ define([
 
     execute: function(callback, args) {
 
+      console.log(Backbone.history);
+
       if (_.isFunction(callback)) {
         callback.apply(this, args);
       }
@@ -126,7 +128,7 @@ define([
           );
         }
       } else {
-        this.getPubSub().publish(this.getPubSub().NAVIGATE, 'index-page');
+        this.getPubSub().publish(this.getPubSub().NAVIGATE, 'index-page', { replace: true });
       }
     },