Camellia: fix compiler warning

* cipher/camellia-glue.c (camellia_setkey): Use braces around empty if
statement.

Patch silences following warning:

camellia-glue.c: In function 'camellia_setkey':
camellia-glue.c:183:5: warning: suggest braces around empty body in an 'if' statement [-Wempty-body]

• Signed-off-by: Jussi Kivilinna <jussi.kivilinna@iki-fi>