qapi: Fix build_params() for empty parameter list

build_params() returns '' instead of 'void' when there are no
parameters.  Can't happen now, but the next commit will change that.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
[peterx: compose the patch from email replies]
Signed-off-by: Peter Xu <peterx@redhat.com>
Message-Id: <20180815133747.25032-3-peterx@redhat.com>
1 file changed