Do not sync empty queues

includes/classes/Indexable.php

@@ -388,6 +388,10 @@ public function bulk_index_dynamically( $object_ids ) {
 
 			$document = $this->prepare_document( $object_id );
 
+			if ( empty( $document ) ) {
+				continue;
+			}
+
 			/**
 			 * Conditionally kill indexing on a specific object
 			 *
@@ -404,6 +408,12 @@ public function bulk_index_dynamically( $object_ids ) {
 			$documents[] = $document_str;
 		}
 
+		if ( empty( $documents ) ) {
+			return [
+				new \WP_Error( 'ep_bulk_index_no_documents', esc_html__( 'It was not possible to create a body request with the document IDs provided.', 'elasticpress' ), $object_ids ),
+			];
+		}
+
 		$results = $this->send_bulk_index_request( $documents );
 
 		/**

includes/classes/SyncManager.php

@@ -205,6 +205,10 @@ public function index_sync_queue() {
 
 		$current_blog_id = get_current_blog_id();
 		foreach ( $this->sync_queue as $blog_id => $sync_queue ) {
+			if ( empty( $sync_queue ) ) {
+				continue;
+			}
+
 			if ( $current_blog_id !== $blog_id ) {
 				switch_to_blog( $blog_id );
 			}