Fixes CID 72320: Explicit NULL dereferenced
On error it is possible that the blocklen_per_process array is
NULL. Change the NULL check before the free to check for non-NULL on
the array not the array element. Also clean up allocation of this
array to use calloc instead of malloc + setting each element to NULL.
Signed-off-by: Nathan Hjelm <hjelmn@lanl.gov>