Fix group runner sort dropdown

Changelog: fixed

app/views/groups/runners/_sort_dropdown.html.haml

-- sorted_by = sort_options_hash[@sort]
+- sorted_by = sort_options_hash[@sort] || sort_title_created_date
 
 .dropdown.inline.gl-ml-3
   %button.dropdown-menu-toggle{ type: 'button', data: { toggle: 'dropdown', display: 'static' } }

spec/views/groups/runners/_sort_dropdown.html.haml_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe 'groups/runners/sort_dropdown.html.haml' do
+  describe 'render' do
+    let_it_be(:sort_options_hash) { { by_title: 'Title' } }
+    let_it_be(:sort_title_created_date) { 'Created date' }
+
+    before do
+      allow(view).to receive(:sort).and_return('by_title')
+    end
+
+    describe 'when a sort option is not selected' do
+      it 'renders a default sort option' do
+        render 'groups/runners/sort_dropdown', sort_options_hash: sort_options_hash, sort_title_created_date: sort_title_created_date
+
+        expect(rendered).to have_content 'Created date'
+      end
+    end
+
+    describe 'when a sort option is selected' do
+      it 'renders the selected sort option' do
+        @sort = :by_title
+        render 'groups/runners/sort_dropdown', sort_options_hash: sort_options_hash, sort_title_created_date: sort_title_created_date
+
+        expect(rendered).to have_content 'Title'
+      end
+    end
+  end
+end