Don't try to show a fallback speaker avatar if there isn't one

get_together/templates/get_together/speakers/create_speaker.html

@@ -10,7 +10,7 @@
 {% csrf_token %}
 <div class="form-group">
     <table class="table">
-        <tr><th></th><td><img src="{{speaker.headshot.url}}"/></td></tr>
+        <tr><th></th><td><img src="{% if speaker.headshot %}{{speaker.headshot.url}}{% endif %}"/></td></tr>
         {{speaker_form}}
     </table>
 	<br />