ui: show error name

packages/ui-default/templates/main.html

@@ -2,6 +2,7 @@
 {% extends "layout/basic.html" %}
 {% import "components/contest.html" as contest with context %}
 {% import "components/problem.html" as problem with context %}
+{% import "components/user.html" as user with context %}
 {% block content %}
 <div class="row">
   {% for column in contents %}