WaE: C4389: '!=' : signed/unsigned mismatch

Change-Id: I6a2e0992077b185107f8d7190478d95f8d898e9e
Reviewed-on: https://gerrit.libreoffice.org/9266
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>
Tested-by: Stephan Bergmann <sbergman@redhat.com>