Kepler

Workflow: There are two composite actors, one called CompositeActor1 on the top level, another called CompositeActor2, in CompositeActor1. There are two String Parameters: one called p1 on the top level, another called p2 with value '$p1/l', in CompositeActor1. p2 is used in actors in CompositeActor1, such as expression, file open.

Steps:
1) Open the whole workflow,
2) Open CompositeActor1,
3) Open CompositeActor2,
4) Close CompositeActor2,
5) Delete CompositeActor2,
6) Change the value of p1.

There will be an error saying that: "Error evaluating expression: $p1/l in .CompositeActor2.p2 Because The ID p1 is undefined."

There is no way to close the error except closing Kepler by force, which will lost all unsaved modification.

I found the bug with Kepler version 16865 and ptolemy version 52661, but I think this bug is always there.

I attached the workflow and error dialogue.