Fix twitter links

Author: geoah

_layouts/event.html

@@ -25,7 +25,7 @@ <h3><small>{{ presentation.date | date: "%H:%M" }}</small> {{ presentation.title
     </div>
     <div class="row">
       <div class="">
-        <h6>by {% if presentation.author.twitter != "" %}<a href="https://twitter.com/{{ presentation.author.twitter }}" target="_blank">{{ presentation.author.name }}</a>{% else %}{{ presentation.author.name }}{% endif %}</h6>
+        <h6>by {% if presentation.author.twitter %}<a href="https://twitter.com/{{ presentation.author.twitter }}" target="_blank">{{ presentation.author.name }}</a>{% else %}{{ presentation.author.name }}{% endif %}</h6>
         <br />
       </div>
     </div>

events.html

@@ -42,7 +42,7 @@ <h5>{{ event.date | date: "%b %-d, %Y" }} @{{ event.location}}</h5>
           <div class="inner">
             <h6>{{ presentation.title }}</h6>
             <p>{{ presentation.description }}</p>
-            <p><em>— {% if presentation.author.twitter != "" %}<a href="https://twitter.com/{{ presentation.author.twitter }}" target="_blank">{{ presentation.author.name }}</a>{% else %}{{ presentation.author.name }}{% endif %}</em></p>
+            <p><em>— {% if presentation.author.twitter %}<a href="https://twitter.com/{{ presentation.author.twitter }}" target="_blank">{{ presentation.author.name }}</a>{% else %}{{ presentation.author.name }}{% endif %}</em></p>
           </div>
         </div>
         {% endfor %}