nfsd4: fix bare destroy_session null dereference

It's legal to send a DESTROY_SESSION outside any session (as the only
operation in a compound), in which case cstate->session will be NULL;
check for that case.

While we're at it, move these checks into a separate helper function.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
1 file changed