Description of problem:
Using a regular expression in a report filter corrupts the filter and renders the report useless.


Version-Release number of selected component (if applicable):
5.8.1.5.20170725160636_e433fc0

How reproducible:
100%


Steps to Reproduce:
1. Create a new reports based on VMs and Instances, call it Corrupted Report
2. Add 'Name' as a column. More fields could be added but it is not necessary
3. Switch to filter tab and craft the following conditional:
   VM and Instance : Vendor REGULAR EXPRESSION MATCHES "openstack"
4. Check the checkbox
5. Click on the conditional as if to edit it and watch things break
6. Your report is now corrupted

Actual results:
Upon clicking the conditional the following error is displayed:

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 

Now the 

Expected results:
No error should be displayed and the report should not be corrupted.

Additional info:
I am marking this as medium sev because the workaround is to blow away the report and start from scratch again.