Update submodules: plugins (new commits)

plugins:
    b0b09c3 Greg Holmes <greg@dmdirc.com>
            Check for rare condition where clipboard doesn't exist.

            Fixes-Issue: CLIENT-503
            Gerrit: http://gerrit.dmdirc.com/3388

Change-Id: I6648b54c137a6399c2a9fd03e3ea680c42e2497e