fix problem with gcc compiler complaining on variable type

Change-Id: I9a16e24e79d22b0af1710d6ac25eaa5fb19c71ff
Reviewed-on: https://gerrit.libreoffice.org/12047
Reviewed-by: Noel Grandin <noelgrandin@gmail.com>
Tested-by: Noel Grandin <noelgrandin@gmail.com>