Fix diff files being visible in the diff file header

app/assets/javascripts/diffs/components/diff_stats.vue

@@ -17,7 +17,7 @@ export default {
     diffFilesLength: {
       type: Number,
       required: false,
-      default: 0,
+      default: null,
     },
   },
   computed: {

spec/frontend/diffs/components/diff_stats_spec.js

@@ -3,6 +3,18 @@ import Icon from '~/vue_shared/components/icon.vue';
 import DiffStats from '~/diffs/components/diff_stats.vue';
 
 describe('diff_stats', () => {
+  it('does not render a group if diffFileLengths is empty', () => {
+    const wrapper = shallowMount(DiffStats, {
+      propsData: {
+        addedLines: 1,
+        removedLines: 2,
+      },
+    });
+    const groups = wrapper.findAll('.diff-stats-group');
+
+    expect(groups.length).toBe(2);
+  });
+
   it('does not render a group if diffFileLengths is not a number', () => {
     const wrapper = shallowMount(DiffStats, {
       propsData: {