Show the word "None" when dropdowns are empty

mayan/apps/appearance/templatetags/appearance_tags.py

@@ -1,6 +1,7 @@
 from __future__ import unicode_literals
 
 from django.template import Library
+from django.utils.translation import ugettext_lazy as _
 
 register = Library()
 
@@ -11,3 +12,5 @@ def get_choice_value(field):
         return dict(field.field.choices)[field.value()]
     except TypeError:
         return ', '.join([entry for id, entry in field.field.choices])
+    except KeyError:
+        return _('None')