libpromises: initialize variable, avoid gcc warning
(cherry picked from commit 5da3942d735ff6b6b930fd94f7f9002e826b9fff)
server.c: after refusing transfer access, exit the function

Why would we want to continue with the flow and open the file?
(cherry picked from commit 11e4c94f97d41f70cae16b64d2a30ffb9f1ac49a)