Funny, just ran into this when I inadvertently pointed the database connections to the ports for a non-running pgpool. The message (to help anyone else searching for this bug) was:
Use of uninitialized value $nbytes in numeric eq (==) at /usr/local/share/perl5/OpenSRF/Transport/SlimJabber/XMPPReader.pm line 229.
Your patch sorted things right away. Committed to master.