Block Hooks: Return early from saving meta data for the navigation without a $post->ID

packages/block-library/src/navigation/index.php

@@ -1512,6 +1512,14 @@ function block_core_navigation_set_ignored_hooked_blocks_metadata( $inner_blocks
  * @return stdClass The updated post object.
  */
 function block_core_navigation_update_ignore_hooked_blocks_meta( $post ) {
+	/*
+	 * In this scenario the user has likely tried to create a navigation via the REST API.
+	 * In which case we won't have a post ID to work with and store meta against.
+	 */
+	if ( ! isset( $post->ID ) ) {
+		return $post;
+	}
+
 	/*
 	 * We run the Block Hooks mechanism to inject the `metadata.ignoredHookedBlocks` attribute into
 	 * all anchor blocks. For the root level, we create a mock Navigation and extract them from there.

phpunit/blocks/block-navigation-block-hooks-test.php

@@ -92,4 +92,25 @@ public function test_block_core_navigation_update_ignore_hooked_blocks_meta_pres
 			'Block was not added to ignored hooked blocks metadata.'
 		);
 	}
+
+	/**
+	 * @covers ::gutenberg_block_core_navigation_update_ignore_hooked_blocks_meta
+	 */
+	public function test_block_core_navigation_rest_creation() {
+		wp_set_current_user( 1 );
+
+		$post_type_object = get_post_type_object( 'wp_navigation' );
+		$request          = new WP_REST_Request( 'POST', '/wp/v2/' . $post_type_object->rest_base );
+		$request->set_body_params(
+			array(
+				'title'   => 'Title ' . $post_type_object->label,
+				'content' => $post_type_object->label,
+				'_locale' => 'user',
+			)
+		);
+		$response = rest_get_server()->dispatch( $request );
+
+		$this->assertNotEmpty( $response->get_status() );
+		$this->assertSame( 201, $response->get_status() );
+	}
 }