This patch adds a sanity check so that names passed into
rte_metrics_reg_names() and the wrapper rte_metrics_reg_name()
cannot be NULL.
Fixes: 349950ddb9c5 ("metrics: add information metrics library")
Cc: stable@dpdk.org
Signed-off-by: Remy Horton <remy.horton@intel.com>
Acked-by: Ferruh Yigit <ferruh.yigit@intel.com>