Return an empty object when no fallback templates are found (wp/v2/te…

…mplates/lookup) (#60925)

Unlinked contributors: oryfoxer.

Co-authored-by: creativecoder <grantmkin@git.wordpress.org>
Co-authored-by: joemcgill <joemcgill@git.wordpress.org>
Co-authored-by: t-hamano <wildworks@git.wordpress.org>
Co-authored-by: david-binda <davidbinda@git.wordpress.org>

lib/compat/wordpress-6.6/class-gutenberg-rest-templates-controller-6-6.php

@@ -113,7 +113,8 @@ public function get_template_fallback( $request ) {
 			array_shift( $hierarchy );
 		} while ( ! empty( $hierarchy ) && empty( $fallback_template->content ) );
 
-		$response = $this->prepare_item_for_response( $fallback_template, $request );
+		// To maintain original behavior, return an empty object rather than a 404 error when no template is found.
+		$response = $fallback_template ? $this->prepare_item_for_response( $fallback_template, $request ) : new stdClass();
 
 		return rest_ensure_response( $response );
 	}

packages/core-data/src/resolvers.js

@@ -712,7 +712,8 @@ export const getDefaultTemplateId =
 		const template = await apiFetch( {
 			path: addQueryArgs( '/wp/v2/templates/lookup', query ),
 		} );
-		if ( template ) {
+		// Endpoint may return an empty object if no template is found.
+		if ( template?.id ) {
 			dispatch.receiveDefaultTemplateId( query, template.id );
 		}
 	};

packages/edit-post/src/store/selectors.js

@@ -609,10 +609,13 @@ export const getEditedPostTemplate = createRegistrySelector(
 		const defaultTemplateId = select( coreStore ).getDefaultTemplateId( {
 			slug: slugToCheck,
 		} );
-		return select( coreStore ).getEditedEntityRecord(
-			'postType',
-			'wp_template',
-			defaultTemplateId
-		);
+
+		return defaultTemplateId
+			? select( coreStore ).getEditedEntityRecord(
+					'postType',
+					'wp_template',
+					defaultTemplateId
+			  )
+			: null;
 	}
 );