Pigeonhole 0.4.4 error with no sieve rules

I have built and installed Pigeonhole 0.4.4 with Dovecot 2.2.15. For users with no sieve at all I am getting an error on delivery. Delivery is from exim via lmtp.

Syslog: Oct 28 11:03:50 mailhost dovecot: [ID 583609 mail.crit] lmtp(18915): Fatal: master: service(lmtp): child 18915 killed with signal 11 (core not dumped - set service lmtp { drop_priv_before_exec=yes })

There is no global sieve script because there is no global sieve rule. Where an account has sieve rules delivery works as expected. To make it work again I've gone back to 2.2.15 with 0.4.3.

James.