Fix the registration issue that was reported by Andrea Suisani IAX_EVENT_NULL was interpreted as a registration reply and thus the  registration session management got confused.
Fix the registration issue that was reported by Andrea Suisani
IAX_EVENT_NULL was interpreted as a registration reply and thus the 
registration session management got confused.


git-svn-id: 9ed0004971709408f906b8bdafa7f98a7bcab630@1212 f854266a-e20d-0410-a9be-8852184c940f

zlargon/iaxclient,zlargon/iaxclient,zlargon/iaxclient,zlargon/iaxclient,zlargon/iaxclient