audit log entry for null CAS service

[Andrew Morgan]

When a client requests the CAS login page without providing a service, the 
IDP returns an error page "An error occurred: ServiceNotSpecified" and 
HTTP code 500.  However, it also logs that in the audit log.

Apache log entry:

67.217.233.218 - - [12/Nov/2017:00:01:52 -0800] "GET /idp/profile/cas/login HTTP/1.1" 500 6695

idp-audit.log:

20171112T080152Z|67.217.233.218||||https://www.apereo.org/cas/protocol/login|||||||||


Is there a reason for the audit log entry?  That seems like a bug to me.

I'm running IDP v3.3.1.

Thanks,
 	Andy