Use ... for badge text when actual count is unknown

See https://gitlab.com/gitlab-org/gitlab-ce/issues/34336

app/assets/javascripts/issuable/related_issues/components/related_issues_block.vue

@@ -76,8 +76,8 @@ export default {
     hasBody() {
       return this.isFormVisible || this.shouldShowTokenBody;
     },
-    relatedIssueCount() {
-      return this.relatedIssues.length;
+    badgeLabel() {
+      return this.isFetching && this.relatedIssues.length === 0 ? '...' : this.relatedIssues.length;
     },
     hasHelpPath() {
       return this.helpPath.length > 0;
@@ -113,7 +113,7 @@ export default {
             <span
               class="issue-count-badge-count"
               :class="{ 'has-btn': this.canAddRelatedIssues }">
-              {{ relatedIssueCount }}
+              {{ badgeLabel }}
             </span>
             <button
               v-if="canAddRelatedIssues"

spec/javascripts/issuable/related_issues/components/related_issues_block_spec.js

@@ -64,6 +64,10 @@ describe('RelatedIssuesBlock', () => {
     it('should show loading icon', () => {
       expect(vm.$refs.loadingIcon).toBeDefined();
     });
+
+    it('should show `...` badge count', () => {
+      expect(vm.badgeLabel).toBe('...');
+    });
   });
 
   describe('with canAddRelatedIssues=true', () => {