Merge pull request #15590 from woocommerce/fix/15584

Prevent error in wc_get_product_term_ids

includes/wc-product-functions.php

@@ -883,7 +883,7 @@ function wc_get_related_products( $product_id, $limit = 5, $exclude_ids = array(
  */
 function wc_get_product_term_ids( $product_id, $taxonomy ) {
 	$terms = get_the_terms( $product_id, $taxonomy );
-	return ! empty( $terms ) ? wp_list_pluck( $terms, 'term_id' ) : array();
+	return ( empty( $terms ) || is_wp_error( $terms ) ) ? array() : wp_list_pluck( $terms, 'term_id' );
 }
 
 /**