Don't change alias if the current alias is invalid.

Change-Id: I8a097dec93b28411563895d60a8b0a0f937d9de4
Reviewed-on: http://gerrit.dmdirc.com/3583
Automatic-Compile: DMDirc Build Manager
Reviewed-by: Chris Smith <chris@dmdirc.com>
Add more tests for VetoableListSelectionModel.

Change-Id: Icf602cbe6ed52b3db8ac230cb70a7d331f270ec2
Reviewed-on: http://gerrit.dmdirc.com/3582
Automatic-Compile: DMDirc Build Manager
Reviewed-by: Chris Smith <chris@dmdirc.com>
Remove some uneeded custom classes.

Change-Id: I07ece70b1f5dfd7b36bb8a589ebb472379699ca7
Reviewed-on: http://gerrit.dmdirc.com/3584
Automatic-Compile: DMDirc Build Manager
Reviewed-by: Chris Smith <chris@dmdirc.com>