- fixed longstanding topic desync bug during netbursts, which has been
  reported by several people. We now basically do what ircu does, i.e.
  unset topics set by netriders

git-svn-id: svn://svn.ircd-hybrid.org/svnroot/ircd-hybrid-7.2@873 82007160-df01-0410-b94d-b575c5fd34c7