Update selector to return static menu data if state is not populated …

…from API

client/state/admin-menu/selectors/index.js

@@ -2,6 +2,7 @@
  * Internal dependencies
  */
 import 'state/inline-help/init';
+import fallbackResponse from '../fallback-data.json';
 
 export function getAdminMenu( state, siteId ) {
 	const stateSlice = state?.adminMenu;
@@ -10,5 +11,12 @@ export function getAdminMenu( state, siteId ) {
 		return null;
 	}
 
-	return state.adminMenu[ siteId ] || null;
+	/**
+	 * To ensure that a menu is always available in the UI even
+	 * if the network fails on an uncached request we provide a
+	 * set of static fallback data to render a basic menu. This
+	 * avoids a situation where the user might be left with an
+	 * empty menu.
+	 */
+	return state.adminMenu[ siteId ] || fallbackResponse;
 }

client/state/admin-menu/test/selectors.js

@@ -2,7 +2,7 @@
  * External dependencies
  */
 import deepFreeze from 'deep-freeze';
-
+import fallbackResponse from '../fallback-data.json';
 /**
  * Internal dependencies
  */
@@ -19,20 +19,20 @@ describe( 'selectors', () => {
 			expect( getAdminMenu( state, 123456 ) ).toEqual( null );
 		} );
 
-		test( 'returns null when siteId is not provided', () => {
+		test( 'returns null data when siteId is not provided', () => {
 			const state = {};
 
 			expect( getAdminMenu( state ) ).toEqual( null );
 		} );
 
-		test( 'returns null when requested siteId key is not present', () => {
+		test( 'returns fallback data  when requested siteId key is not present', () => {
 			const state = {
 				adminMenu: {
 					56789: frozenFixture,
 				},
 			};
 
-			expect( getAdminMenu( state, 12345 ) ).toEqual( null );
+			expect( getAdminMenu( state, 12345 ) ).toEqual( fallbackResponse );
 		} );
 
 		test( 'returns menu data when siteId is present', () => {