Description of problem:
ISE in case no system  is selected for deployed configuration files comparison.

Version-Release number of selected component (if applicable):
spacewalk-java-2.0.2-78

How reproducible:
100%

Steps to Reproduce:
1. Create configuration channel.
2. Create a configuration file in it.
3. Register a client to Satellite.
     - add provisioning entitlement.
     - assign the configuration channel to the client.
     - install rhncfg* on the client.
4. Deploy the configuration file on the client.
    $ rhncfg-client get
5. Configuration -> Recently Modified Configuration Files: -> "conf file" ->
     Compare File -> Deployed Files
   Do not select any system, just press "Schedule File Comparison"

Actual results:
ISE

Expected results:
Some message.

Additional info: