Fix SipVia::getTAddr method to return default SIP port instead of None when no specific port has been provided.
Fix SipVia::getTAddr method to return default SIP port instead of None
when no specific port has been provided.

Reported by:	Jinke Jiang

sippy/rtpproxy,sippy/rtp_cluster,jevonearth/rtpproxy,synety-jdebp/rtpproxy,dsanders11/rtpproxy,sippy/rtpproxy,sippy/rtpproxy,dsanders11/rtpproxy,synety-jdebp/rtpproxy,synety-jdebp/rtpproxy,dsanders11/rtpproxy,synety-jdebp/rtpproxy,jevonearth/rtpproxy,jevonearth/rtpproxy,sippy/rtp_cluster,jevonearth/rtpproxy