app/crypto-perf: fix null dereference
app/crypto-perf: fix null dereference

Dereferencing a pointer that might be null key_token when calling strstr.
Check if the pointer is null before.

Coverity issue: 141071
Fixes: f8be1786b1b8 ("app/crypto-perf: introduce performance test application")

Signed-off-by: Slawomir Mrozowicz <e88e38a554fa6ee2c1af7d54e8bb48581354aa35@intel.com>
Acked-by: Pablo de Lara <28355d9cfe41bb8148aea0fb24f47aae8f4217a1@intel.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk