In cases where the a plugin responds with both a null or empty volume
and a null or empty Err, the daemon would panic.
This is because we assumed the idiom if `err` is nil, then `v` must not
be but in reality the plugin may return whatever it wants and we want to
make sure it doesn't harm the daemon.
Signed-off-by: Brian Goff <cpuguy83@gmail.com>
Upstream-commit: 96c79a1934dd52d2a6f648e519b5d4ac60ac8ca1
Component: engine
661cc031a6