Fixed preview macro when hrefs are used in author field (#147)

templates/macros.html

 {% macro preview(lecture) %}
 <li class="list-group-item">
-	<a class="hidden-xs" href="{{url_for('lecture', id=lecture['id'])}}" title="{{ lecture.course.title }}" style="color: #000">
+	<a href="{{url_for('lecture', id=lecture['id'])}}" title="{{ lecture.course.title }}" style="color: #000">
+		<div class="hidden-xs">
 			<div class="row">
 				<img class="col-xs-4" style="max-height: 100px; width: auto;" src="{{ config.VIDEOPREFIX }}/{{ lecture['titlefile'] }}" alt="Vorschaubild" onerror="this.src='{{url_for('static',filename='no-thumbnail.png')}}'; this.onerror=''; ">
 				<div class="col-xs-4">
@@ -16,8 +17,8 @@
 					<p style="font-style: italic; color: #777;">{{ lecture['comment']|fixnl|safe }}</p>
 				</div>
 			</div>
-	</a>
-	<a class="visible-xs" href="{{url_for('lecture', id=lecture['id'])}}" title="{{ lecture.course.title }}" style="color: #000">
+		</div>
+		<div class="visible-xs">
 			<ul class="list-unstyled">
 				<li>
 					<img style="width: 100%;" src="{{ config.VIDEOPREFIX }}/{{ lecture['titlefile'] }}" alt="Vorschaubild" onerror="this.src='{{url_for('static',filename='no-thumbnail.png')}}'; this.onerror=''; ">
@@ -37,6 +38,7 @@
 					<p style="font-style: italic; color: #777;">{{ lecture['comment']|fixnl|safe }}</p>
 				</li>
 			</ul>
+		</div>
 	</a>
 </li>