Fixed admin_1 errors in the logs

Fixed errors when trying to log in with an account without domain.
This closes #585

core/admin/mailu/models.py

@@ -35,11 +35,14 @@ class IdnaEmail(db.TypeDecorator):
     impl = db.String(255, collation="NOCASE")
 
     def process_bind_param(self, value, dialect):
+        try:
             localpart, domain_name = value.split('@')
             return "{0}@{1}".format(
                 localpart,
                 idna.encode(domain_name).decode('ascii'),
             )
+        except:
+            pass
 
     def process_result_value(self, value, dialect):
         localpart, domain_name = value.split('@')