mgmt-tester: Fix build error

mgmt-tester: Fix build error

This fixes the following build error:

CC    tools/mgmt-tester.o
tools/mgmt-tester.c: In function ‘setup_command_generic’:
tools/mgmt-tester.c:7503:16: error: the comparison will always evaluate
as ‘true’ for the pointer operand in
‘(const struct setup_mgmt_cmd *)test->setup_mgmt_cmd_arr +
(sizetype)(i * 24)’ must not be NULL [-Werror=address]
 7503 |     for (; test->setup_mgmt_cmd_arr + i; ++i) {
   |        ^~~~

Signed-off-by: Manika Shrivastava <manika.sh@samsung.com>
Signed-off-by: Ayush Garg <ayush.garg@samsung.com>