For some reason, e.g. Clang 3.8.1 doesn't evaluate std::strlen here (though it
apparently does in other places in this file).

Change-Id: Ib2b7dcc1d7b6ae47ef285bd2edb65e399dc11b79
Reviewed-on: https://gerrit.libreoffice.org/33547Reviewed-by: Stephan Bergmann <sbergman@redhat.com>
Tested-by: Stephan Bergmann <sbergman@redhat.com>