memory allocation error

[marcstern]

in jwe.c, on line 1952:

cek = cjose_get_alloc()(cek_len);
memcpy(cek, jwe->cek, cek_len);

Allocation result is not checked. We should add

if (!cek) {
   CJOSE_ERROR(err, CJOSE_ERR_NO_MEMORY);
   return NULL;
}

[zandbelt]

this is now part of the maintenance fork here: https://github.com/OpenIDC/cjose/tree/version-0.6.2.x