nua_stack.c: do not use empty tag parameter with To header.
nua_stack.c: do not use empty tag parameter with To header.

darcs-hash:20060817183652-65a35-e01371ecf7dd7af3ff6d79eabf8b5b856b6e2af4.gz

erdincay/sofia-sip,jart/sofia-sip,unispeech/sofia-sip,BelledonneCommunications/sofia-sip,jart/sofia-sip,xhook/sofia-sip,xhook/sofia-sip,jart/sofia-sip,erdincay/sofia-sip,unispeech/sofia-sip,BelledonneCommunications/sofia-sip,erdincay/sofia-sip,unispeech/sofia-sip,BelledonneCommunications/sofia-sip,erdincay/sofia-sip,xhook/sofia-sip,BelledonneCommunications/sofia-sip,unispeech/sofia-sip,xhook/sofia-sip,xhook/sofia-sip