*Steps to reproduce:*
# Create and open an empty project and install com.unity.behavior
# Create and open a behavior graph (Assets > Create > Behavior > Behavior Graph)
# Add a "GameObject" blackboard variable
# In the scene hierarchy, create a new game object
# Add a behavior agent component
# Assign the graph
# Make two other prefabs (prefab1 and prefab2) and assign prefab1 to the variable on the scene game object agent (make sure you select the "Assets" tab in the object picker)
# Drag and drop the game object to the project view to make a prefab out of it
# Assign prefab2 to the variable on the scene game object agent
# Apply the changes to the prefab by right-clicking on the component (see video)
# Click on the prefab in the project view and observe the value of the blackboard variable

*Actual results:* The blackboard variable on the agent prefab references prefab1

*Expected results:* The blackboard variable on the agent prefab references prefab2

*Reproducible with versions:* 1.0.8

*Tested on (OS):* MacOS