fixed graph component spec

spec/javascripts/pipelines/graph/graph_component_spec.js

@@ -101,7 +101,7 @@ describe('graph component', function () {
 
   describe('when linked pipelines are not present', function () {
     beforeEach(function () {
-      const pipeline = Object.assign(graphJSON, { triggered: [], triggered_by: [] });
+      const pipeline = Object.assign(graphJSON, { triggered: null, triggered_by: null });
       this.component = new GraphComponent({
         propsData: { pipeline, isLoading: false },
       }).$mount();