BUG: ERROR: regcomp failed with error empty (sub)expression

What does this error message means ?

I did a query:
discovery=> select a.msg_id,b.key_id into qq from publications a, keywords b where a.title ~* b.name and b.key_id in ( select key_id from keywords);
ERROR: regcomp failed with error empty (sub)expression

I found what's the problem:

in a.title ~* b.name b.name = '' (NOT NULL)

discovery=> select * from keywords where key_id=449;
key_id|name
------+----
449|
(1 row)

I consider this as a bug in regcomp code. rexx, perl match empty string !

This happens with slightly outdated (week ago) 6.5 cvs

Regards,

Oleg
_____________________________________________________________
Oleg Bartunov, sci.researcher, hostmaster of AstroNet,
Sternberg Astronomical Institute, Moscow University (Russia)
Internet: oleg(at)sai(dot)msu(dot)su, http://www.sai.msu.su/~megera/
phone: +007(095)939-16-83, +007(095)939-23-83