Custom conditions sometimes make the editor unresponsive

[Bretterteig]

We are utilising munki's custom conditions feature with predicates that are not know to the built-in predicate editor.
We noticed that the interface sometimes becomes unresponsive when trying to edit some custom predicates.

How to reproduce:

• Create a custom condition with the following content: NOT(Apps CONTAINS "Test")
• Open the editor again and click on "ok"
• The windows will move to the back and no further input is possible.

[pnerum]

I'm also experiencing the same issue.