pg_dump 9.1.1 hanging (collectSecLabels gets 0 labels)

We have a cluster running 9.1.1 where pg_dump hangs when we try to dump 
some a database inside of the cluster.  The server is running AIX.

I can see this on clean cluster where we do an initdb, followed by a 
createdb and try running pg_dump.

I've tracked the issue down to collectSecLabels in pg_dump.c

SELECT label, provider, classoid, objoid, objsbid FROM 
pg_catalog.pg_seclabel;

returns 0 rows.

The code in collectSecLabels() is not prepared to deal with a zero row 
result and tries to malloc 0 bytes.

I am not yet sure if the problem is that my pg_seclabel is empty or if 
the issue is in collectSecLabels() or if collectSecLabels shouldn't even 
be called.

Has anyone seen something similar?