Refactor dispatcher dashboard mr path

app/assets/javascripts/dispatcher.js

@@ -209,8 +209,9 @@ import Activities from './activities';
             .catch(fail);
           break;
         case 'dashboard:merge_requests':
-          projectSelect();
-          initLegacyFilters();
+          import('./pages/dashboard/merge_requests')
+            .then(callDefault)
+            .catch(fail);
           break;
         case 'groups:issues':
         case 'groups:merge_requests':

app/assets/javascripts/pages/dashboard/merge_requests/index.js

+import projectSelect from '~/project_select';
+import initLegacyFilters from '~/init_legacy_filters';
+
+export default () => {
+  projectSelect();
+  initLegacyFilters();
+};