Description of problem:

Adding a non-existing system to a group through the web UI triggers 500 internal server error rather than an error message

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

0.13 (pre-release build)

How reproducible:

Always

Steps to Reproduce:
1. Go to the groups
2. Enter a non-existent system name in the Systems box
3. Hit "Add"

Actual results:

Internal server error

Expected results:

Error message stating there is no such system