Update submodules: plugins (new commits)

plugins:
    293ee29 Greg Holmes <greg@dmdirc.com>
            If the dialog is empty, don't try to update rows.

            Fixes-Issue: CLIENT-487
            Gerrit: http://gerrit.dmdirc.com/3316

Change-Id: I28236bd8f2a758e323236a8509e9788011532d56