Blackboard variable of type List<CustomUnityObject> throws errors in Blackboard

Steps to reproduce:

1. Create a new "MyCustomAgent" Monobehavior
2. Create an custom action "Get Agent in AgentList" and set AgentList as a List<GameObject>
3. Open the new action (from code) and change the type of the list to be List<MyCustomAgent>
4. Go back in the graph and create a blackboard variable from the AgentList field

Actual results: 

• the blackboard view doesn't let you set default value for list items
• an error in throw in the console ("No UI type found for TypedVariableModel`1.")

Expected results: 

• No error is throw
• It is possible to set default value for the list from the blackboard view

Reproducible with versions: 
1.0.0; 1.0.11