The empty clause was originally introduced to set a cutoff settings as a
hack at a commit ae862c16a and later removed at a commit a89470d2e. At
this time, the clause became empty but another commit aa58b9cf5 reuse
the clause and finally a commit 9baedb1c6 removes so that the clause is
empty now.
Norihiro Kamae
8938aeebfa