forms: the assigned value is never used

Change-Id: I8eadc27ba8880630ec93c68145969f3e8ba6c189
Reviewed-on: https://gerrit.libreoffice.org/11712
Reviewed-by: Noel Grandin <noelgrandin@gmail.com>
Tested-by: Noel Grandin <noelgrandin@gmail.com>