LU-18762 lnet: lst SIGSEGV in parser.c

LU-18762 lnet: lst SIGSEGV in parser.c

A null pointer problem. Null pointer was passed instead of command
structure array. Built in additional chack.

Test-Parameters: trivial
Signed-off-by: Frank Sehr <fsehr@whamcloud.com>
Change-Id: I7d4e44170aeb8e44c55de681b6b3def781a0b1bd
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/58269
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Cyril Bordage <cbordage@whamcloud.com>
Reviewed-by: Manish Regmi <mregmi@ddn.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>