Use parentheses to clarify the code.

Change-Id: I864dc6dacadb5b9ba9dca8e0abd9fa4e6db1eddc
Reviewed-on: https://gerrit.libreoffice.org/25677Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: jan iversen <jani@documentfoundation.org>
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>