Skip if the sending port returned is empty
Skip if the sending port returned is empty

linus-sherrill/sprokit,linus-sherrill/sprokit,linus-sherrill/sprokit,Kitware/sprokit,mathstuf/sprokit,Kitware/sprokit,Kitware/sprokit,Kitware/sprokit,linus-sherrill/sprokit,mathstuf/sprokit,mathstuf/sprokit,mathstuf/sprokit