Avoid errors for post types without a 'menu_icon' (#64015)

Unlinked contributors: karan4official.

Co-authored-by: Mamaduka <mamaduka@git.wordpress.org>
Co-authored-by: t-hamano <wildworks@git.wordpress.org>

packages/edit-site/src/components/add-new-template/utils.js

@@ -166,9 +166,11 @@ export function usePostTypeArchiveMenuItems() {
 						// `icon` is the `menu_icon` property of a post type. We
 						// only handle `dashicons` for now, even if the `menu_icon`
 						// also supports urls and svg as values.
-						icon: postType.icon?.startsWith( 'dashicons-' )
-							? postType.icon.slice( 10 )
-							: archive,
+						icon:
+							typeof postType.icon === 'string' &&
+							postType.icon.startsWith( 'dashicons-' )
+								? postType.icon.slice( 10 )
+								: archive,
 						templatePrefix: 'archive',
 					};
 				} ) || [],
@@ -272,9 +274,11 @@ export const usePostTypeMenuItems = ( onClickMenuItem ) => {
 						// `icon` is the `menu_icon` property of a post type. We
 						// only handle `dashicons` for now, even if the `menu_icon`
 						// also supports urls and svg as values.
-						icon: icon?.startsWith( 'dashicons-' )
-							? icon.slice( 10 )
-							: post,
+						icon:
+							typeof icon === 'string' &&
+							icon.startsWith( 'dashicons-' )
+								? icon.slice( 10 )
+								: post,
 						templatePrefix: templatePrefixes[ slug ],
 				  };
 			const hasEntities = postTypesInfo?.[ slug ]?.hasEntities;

packages/editor/src/store/private-selectors.js

@@ -110,7 +110,10 @@ export const getPostIcon = createRegistrySelector(
 			// `icon` is the `menu_icon` property of a post type. We
 			// only handle `dashicons` for now, even if the `menu_icon`
 			// also supports urls and svg as values.
-			if ( postTypeEntity?.icon?.startsWith( 'dashicons-' ) ) {
+			if (
+				typeof postTypeEntity?.icon === 'string' &&
+				postTypeEntity.icon.startsWith( 'dashicons-' )
+			) {
 				return postTypeEntity.icon.slice( 10 );
 			}
 			return pageIcon;