LU-17000 coverity: Fix Dereference after null under client.c

LU-17000 coverity: Fix Dereference after null under client.c

This patch fixes Dereference after null check reported
by coverity run.

CoverityID: 404748 ("Dereference after null check")

Fixes: 0f2bc318d7 ("LU-15246 ptlrpc: per-device adaptive timeout parameters")
Signed-off-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Change-Id: Id26de5e700b0a420168b359b050d739222574bd2
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/52901
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Timothy Day <timday@amazon.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>