fix one compilation warning in MSVC

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@6961 8aca7d54-2c30-db11-9de9-000461428c89
oN DEFAULT HIDE deletion buttons until show_delte_buttons =1 is set in simuconf.tab

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@6962 8aca7d54-2c30-db11-9de9-000461428c89