REST API: In `WP_REST_Block_Directory_Controller::get_items()`, make sure the blocks data for a plugin is not empty before proceeding.

This avoids a PHP notice if the API returns a plugin with empty data for `blocks` key.

Props khag7, TwentyZeroTwo, justinahinon, TimothyBlynJacobs, dd32, SergeyBiryukov.
Merges [48842] to the 5.5 branch.
Fixes #51018.
Built from https://develop.svn.wordpress.org/branches/5.5@48849


git-svn-id: http://core.svn.wordpress.org/branches/5.5@48611 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/rest-api/endpoints/class-wp-rest-block-directory-controller.php

@@ -95,6 +95,11 @@ class WP_REST_Block_Directory_Controller extends WP_REST_Controller {
 		$result = array();
 
 		foreach ( $response->plugins as $plugin ) {
+			// If the API returned a plugin with empty data for 'blocks', skip it.
+			if ( empty( $plugin['blocks'] ) ) {
+				continue;
+			}
+
 			$data     = $this->prepare_item_for_response( $plugin, $request );
 			$result[] = $this->prepare_response_for_collection( $data );
 		}

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.5.1-alpha-48833';
+$wp_version = '5.5.1-alpha-48849';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.