Ticket #27317: admin-includes-user.php.patch

user.php

@@ -176 +176 @@
                 $user_id = wp_update_user( $user );
         } else {
                 $user_id = wp_insert_user( $user );
-                wp_new_user_notification( $user_id, isset( $_POST['send_password'] ) ? wp_unslash( $pass1 ) : '' );
+                if (!is_wp_error($user_id))
+                        wp_new_user_notification( $user_id, isset( $_POST['send_password'] ) ? wp_unslash( $pass1 ) : '' );
         }
         return $user_id;
 }