[FIX] web_kanban: creation of a "team.user"

When creating a team.user record, there was an error to generate an url
for the image because the attribute "__last_update" didn't exist
on the record.

opw:653725

addons/web_kanban/static/src/js/kanban_record.js

@@ -129,7 +129,7 @@ var KanbanRecord = Widget.extend({
             if (!id) { id = undefined; }
             if (options.preview_image)
                 field = options.preview_image;
-            var unique = this.record.__last_update.value.replace(/[^0-9]/g, '');
+            var unique = this.record.__last_update && this.record.__last_update.value.replace(/[^0-9]/g, '');
             url = session.url('/web/image', {model: model, field: field, id: id, unique: unique});
             if (cache !== undefined) {
                 // Set the cache duration in seconds.