zulip/static/templates/topic_list_item.handlebars

<li class='{{#if is_zero}}zero-subject-unreads{{/if}} {{#if is_muted}}muted_topic{{/if}} topic-list-item' data-name='{{topic_name}}'>
    <span class='topic-box'>
        <a href='{{url}}' class="topic-name">
            {{topic_name}}
        </a>
        <div class="subject_count {{#if is_zero}}zero_count{{/if}}">
            <div class="value">{{unread}}</div>
        </div>
    </span>
    <span class="arrow topic-sidebar-arrow">
        <i class="icon-vector-chevron-down"></i>
    </span>
</li>