Description of problem: While creating compliance policy for VM, an edit of the condition under scope is throwing an error.

Error--> "There is an error in the selected expression element, perhaps it was imported or edited manually.
This element should be removed and recreated or you can report the error to your CFME administrator.
Error details: undefined method `[]' for nil:NilClass "


Version-Release number of selected component (if applicable): 5.8.0.12-rc1.20170425180304_4f35996


How reproducible:100%


Steps to Reproduce:
1. Navigate to Control --> Explorer
2. Create Compliance Policy and under scope add condition/crieteria
3. After adding condition/crieteria and click on it to edit.

Actual results: Throws error mentioned in description


Expected results: It should be able to edit without any error.


Additional info: