[Serusers] Possible bug in pa module

Hello. I think I have found a bug in pa module. If I send a SUBSCRIBE request without an Expires header, pa module rejects it with a 400 response. However, RFC 3265 states: "SUBSCRIBE requests SHOULD contain an Expires header. [...] If no Expires header is present in a SUBSCRIBE request, the implied default is defined by the event package being used." So, pa module should accept subscriptions without an expires header, but it doesn't now. This is quite upsetting, as some clients (Windows Messenger, for example) don't include this header on its SUBSCRIBE requests, and so these requests are rejected by SER. Please correct me if I'm mislead. Regards. Daniel Machín.