Add a simple isEmpty to check when populating the mode panels in the CSD and
display helpful text to the end user.

Change-Id: I02953926148aec1a3ec3504deef55b1b161a9428
Reviewed-on: http://gerrit.dmdirc.com/994
Automatic-Compile: DMDirc Local Commits <dmdirc@googlemail.com>
Reviewed-by: Chris Smith <chris@dmdirc.com>