Make `Photo.author` a @property; None if no author.

etiquette/objects.py

@@ -591,7 +591,13 @@ class Photo(ObjectBase):
         albums = [self.photodb.get_album(f[0]) for f in fetch]
         return albums
 
+    @property
     def author(self):
+        '''
+        Return the User object who owns this photo, or None if it is unassigned.
+        '''
+        if self.author_id is None:
+            return None
         return self.photodb.get_user(id=self.author_id)
 
     def bytestring(self):

frontends/etiquette_flask/templates/photo.html

@@ -184,8 +184,8 @@
         </h4>
         <ul id="metadata">
         <li>Filename: {{photo.basename}}</li>
-        {% if photo.author_id %}
-            {% set author = photo.author() %}
+        {% set author = photo.author %}
+        {% if author is not none %}
             <li>Author: <a href="/user/{{author.username}}">{{author.username}}</a></li>
         {% endif %}
         {% if photo.width %}