Fix NPE in FD notifications plugin.

We had two instances of the FDManager around - one for the command and
once owned by the plugin. The command's instance was never loaded so
had no icon.

Change-Id: I525781a1ede263cbb0ee27f4fb0114dcded2245a
Fixes-Issue: CLIENT-471
Reviewed-on: http://gerrit.dmdirc.com/3231
Reviewed-by: Greg Holmes <greg@dmdirc.com>
Automatic-Compile: DMDirc Build Manager