Fix type check

Author: mikecote

x-pack/examples/alerting_example/public/alert_types/always_firing.tsx

@@ -22,6 +22,7 @@ export function getAlertType(): AlertTypeModel {
     name: 'Always Fires',
     description: 'Alert when called',
     iconClass: 'bolt',
+    documentationUrl: null,
     alertParamsExpression: AlwaysFiringExpression,
     validate: (alertParams: AlwaysFiringParamsProps['alertParams']) => {
       const { instances } = alertParams;

x-pack/examples/alerting_example/public/alert_types/astros.tsx

@@ -47,6 +47,7 @@ export function getAlertType(): AlertTypeModel {
     name: 'People Are In Space Right Now',
     description: 'Alert when people are in space right now',
     iconClass: 'globe',
+    documentationUrl: null,
     alertParamsExpression: PeopleinSpaceExpression,
     validate: (alertParams: PeopleinSpaceParamsProps['alertParams']) => {
       const { outerSpaceCapacity, craft, op } = alertParams;

x-pack/test/functional_with_es_ssl/fixtures/plugins/alerts/public/plugin.ts

@@ -31,6 +31,7 @@ export class AlertingFixturePlugin implements Plugin<Setup, Start, AlertingExamp
       name: 'Test Always Firing',
       description: 'Always fires',
       iconClass: 'alert',
+      documentationUrl: null,
       alertParamsExpression: () => React.createElement('div', null, 'Test Always Firing'),
       validate: () => {
         return { errors: {} };
@@ -43,6 +44,7 @@ export class AlertingFixturePlugin implements Plugin<Setup, Start, AlertingExamp
       name: 'Test Noop',
       description: `Doesn't do anything`,
       iconClass: 'alert',
+      documentationUrl: null,
       alertParamsExpression: () => React.createElement('div', null, 'Test Noop'),
       validate: () => {
         return { errors: {} };