rand.erl: fix PairList declaration in alg_handler()
rand.erl: fix PairList declaration in alg_handler()

* All elements in alg_handler() MUST present
* See <https://github.com/erlang/otp/pull/1235/files/5409c216e74addda541f1d68d8d0f53abab150cb#r86525108>

jj1bdx/emprng,jj1bdx/emprng