Fix CTCP responses.

Only squelsh the response if the event *has* been handled by
something else.

Change-Id: I173e89c26470c1f605ce56f3e6c04b0d29476b35
Reviewed-on: http://gerrit.dmdirc.com/3639
Reviewed-by: Greg Holmes <greg@dmdirc.com>
Automatic-Compile: DMDirc Build Manager