fbarray: fix potential null-dereference
fbarray: fix potential null-dereference

We get pointer to mask before we check if fbarray is NULL. Fix
by moving getting mask pointer to until after NULL check.

Coverity issue: 272579
Fixes: c44d09811b40 ("eal: add shared indexed file-backed array")

Signed-off-by: Anatoly Burakov <814e00d8f6e4e81b7ccc7e3e5a0bfec0078f0203@intel.com>
Acked-by: Adrien Mazarguil <9d39ea493ca46c560334f650ac5d4b5ffbcb5cf0@6wind.com>

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