[#2394] Fix bug with creating users, introduced in previous commit.

Picked from release-dgu1 branch

ckan/lib/create_test_data.py

@@ -523,7 +523,7 @@ def create_users(cls, user_dicts):
 
     @classmethod
     def _create_user_without_commit(cls, name='', **user_dict):
-        if model.User.by_name(name) or model.User.by_openid(user_dict.get('openid')):
+        if model.User.by_name(name) or (user_dict.get('openid') and model.User.by_openid(user_dict.get('openid'))):
             log.warning('Cannot create user "%s" as it already exists.' % \
                             (name or user_dict['name']))
             return