When listener channel is closed, it becomes always available for
reading: select becomes an active loop which writes default-constructed
events (i.e: empty strings).
Fixes#5766.
Docker-DCO-1.1-Signed-off-by: Arnaud Porterie <arnaud.porterie@gmail.com> (github: icecrime)
Upstream-commit: 8699f53e6a033a7b5b55a2b6356da7c6e220d01f
Component: engine