[Devel] item access is not consistent

[Juha Heinanen]

i started to wonder why i got into syslog an error

May 14 18:05:07 tutpro /usr/sbin/sems_openser[8432]: xl_get_authattr: Error while parsing headers

when i referred to $au in my script.

since Proxy-Authorization header is by no means mandatory in every sip
request, imo no error should be reported, but a null result should be
returned instead.

then i started to read item.c code and found that in some cases an error
is reported when a non-existent item is referred to and -1 is returned.
in some other cases, an error message is issued and a null value is
returned, and in some cases a debug message is issued and a null value
is returned.  there are even cases where an empty value is returned
instead of a null value.

handling of non-existent items needs to be consistent. i propose that
when a non-existent sip message item is referred to, a debug message is
issued and a null value is always returned.

other proposals?  

-- juha