Fix error when loading incident issue with alert

Changelog: fixed

app/assets/javascripts/issue_show/components/incidents/graphql/queries/get_alert.graphql

 query getAlert($iid: String!, $fullPath: ID!) {
   project(fullPath: $fullPath) {
     issue(iid: $iid) {
+      id
       alertManagementAlert {
         iid
         title

spec/features/issues/incident_issue_spec.rb

@@ -3,21 +3,58 @@
 require 'spec_helper'
 
 RSpec.describe 'Incident Detail', :js do
+  let_it_be(:project) { create(:project, :public) }
+  let_it_be(:payload) do
+    {
+      'title' => 'Alert title',
+      'start_time' => '2020-04-27T10:10:22.265949279Z',
+      'custom' => {
+        'alert' => {
+          'fields' => %w[one two]
+        }
+      },
+      'yet' => {
+        'another' => 73
+      }
+    }
+  end
+
+  let_it_be(:user) { create(:user) }
+  let_it_be(:started_at) { Time.now.rfc3339 }
+  let_it_be(:alert) { create(:alert_management_alert, project: project, payload: payload, started_at: started_at) }
+  let_it_be(:incident) { create(:incident, project: project, description: 'hello', alert_management_alert: alert) }
+
   context 'when user displays the incident' do
-    it 'shows the incident tabs' do
-      project = create(:project, :public)
-      incident = create(:incident, project: project, description: 'hello')
+    before do
+      project.add_developer(user)
+      sign_in(user)
 
       visit project_issue_path(project, incident)
       wait_for_requests
+    end
 
+    it 'shows incident and alert data' do
       page.within('.issuable-details') do
         incident_tabs = find('[data-testid="incident-tabs"]')
 
+        aggregate_failures 'shows title and Summary tab' do
           expect(find('h2')).to have_content(incident.title)
           expect(incident_tabs).to have_content('Summary')
           expect(incident_tabs).to have_content(incident.description)
         end
+
+        aggregate_failures 'shows the incident highlight bar' do
+          expect(incident_tabs).to have_content('Alert events: 1')
+          expect(incident_tabs).to have_content('Original alert: #1')
+        end
+
+        aggregate_failures 'shows the Alert details tab' do
+          click_link 'Alert details'
+
+          expect(incident_tabs).to have_content('"title": "Alert title"')
+          expect(incident_tabs).to have_content('"yet.another": 73')
+        end
+      end
     end
   end
 end