Check return value of get_post_meta

includes/utils.php

@@ -434,7 +434,13 @@
  */
 function prepare_meta( $post_id ) {
 	update_postmeta_cache( array( $post_id ) );
-	$meta          = get_post_meta( $post_id );
+	$meta = get_post_meta( $post_id );
+
+	if ( false === $meta ) {
+		return array();
+	}
+
+	$meta = is_array( $meta ) ? $meta : array();
 	$prepared_meta = array();
 	$excluded_meta = excluded_meta();