Rename Roadmap app files to be specific

Rename Roadmap app root component and bootstrap script file to have a
specific name for easier debugging while using sourcemaps in browser.

ee/app/assets/javascripts/epic/epic_tabs.js

 import $ from 'jquery';
-import initRoadmap from 'ee/roadmap/index';
+import initRoadmap from 'ee/roadmap/roadmap_bundle';
 
 export default class EpicTabs {
   constructor() {

ee/app/assets/javascripts/pages/groups/roadmap/show/index.js

 import initFilteredSearch from '~/pages/search/init_filtered_search';
 import FilteredSearchTokenKeysEpics from 'ee/filtered_search/filtered_search_token_keys_epics';
 import initEpicCreateApp from 'ee/epic/epic_bundle';
-import initRoadmap from 'ee/roadmap/index';
+import initRoadmap from 'ee/roadmap/roadmap_bundle';
 
 document.addEventListener('DOMContentLoaded', () => {
   initFilteredSearch({

ee/app/assets/javascripts/roadmap/components/epics_list_section.vue

@@ -152,8 +152,10 @@ export default {
 
       // Check if container height is less than total height of all Epic
       // items combined (AKA list is scrollable).
-      const isListVertScrollable =
-        this.$el.parentElement.offsetHeight < EPIC_ITEM_HEIGHT * (this.epics.length + 1);
+      const offsetHeight = this.$el.parentElement
+        ? this.$el.parentElement.offsetHeight
+        : this.$el.offsetHeight;
+      const isListVertScrollable = offsetHeight < EPIC_ITEM_HEIGHT * (this.epics.length + 1);
 
       // Toggle empty row.
       this.showEmptyRow = !isListVertScrollable;

ee/app/assets/javascripts/roadmap/index.js → ee/app/assets/javascripts/roadmap/roadmap_bundle.js

@@ -12,7 +12,7 @@ import { getTimeframeForPreset, getEpicsPathForPreset } from './utils/roadmap_ut
 
 import createStore from './store';
 
-import roadmapApp from './components/app.vue';
+import roadmapApp from './components/roadmap_app.vue';
 
 Vue.use(Translate);
 

ee/spec/javascripts/roadmap/components/app_spec.js → ee/spec/javascripts/roadmap/components/roadmap_app_spec.js

 import Vue from 'vue';
 
-import appComponent from 'ee/roadmap/components/app.vue';
+import appComponent from 'ee/roadmap/components/roadmap_app.vue';
 import createStore from 'ee/roadmap/store';
 import eventHub from 'ee/roadmap/event_hub';