crypto.c:2748:9: warning: variable 'bn_prime' is used uninitialized whenever '||' condition is true [-Wsometimes-uninitialized]
    if (!get_bn_from_bin(env, argv[0], &bn_verifier)
        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
crypto.c:2758:6: note: uninitialized use occurs here
        if (bn_prime) BN_free(bn_prime);
            ^~~~~~~~
crypto.c:2748:9: note: remove the '||' if its condition is always false
    if (!get_bn_from_bin(env, argv[0], &bn_verifier)
        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The resource was not needed as it was never kept between external
crypto calls.

enif_open_resource_type() must be called even during repeated loading
of same library. Otherwise the resource type will be deallocated
when the old module instance is purged.