Requesting zero bytes from shake previously led to out-of-bounds write
on some platforms.
Signed-off-by: NPatrick Steuer <patrick.steuer@de.ibm.com>
Reviewed-by: NRichard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/9433)

(cherry picked from commit a890ef833d114da3430c2f2efd95e01714704d34)