Fix assumption of existing collection

* When logging in, if a user selects "Import existing collections", the
  system would throw an exception, since Redis would return a NoneType,
  which would then be accessed by json.loads(), which doesn't seem to
  know how to process that.
  This fixes that, by providing a string representing an empty json
  array ("[]"), in place of the NoneType.

1 files changed, 2 insertions, 1 deletions

diff --git a/wqflask/wqflask/user_manager.py b/wqflask/wqflask/user_manager.py
index fd1d56ff..e1920f4e 100644
--- a/wqflask/wqflask/user_manager.py
+++ b/wqflask/wqflask/user_manager.py
@@ -122,7 +122,8 @@ class AnonUser(object):
             return collections
 
     def import_traits_to_user(self):
-        collections_list = json.loads(Redis.get(self.key))
+        result = Redis.get(self.key)
+        collections_list = json.loads(result if result else "[]")
         for collection in collections_list:
             uc = model.UserCollection()
             uc.name = collection['name']