FIX crash on with 64bit pointers

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@6558 8aca7d54-2c30-db11-9de9-000461428c89
FIX: crash deleting line in line management window

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@6559 8aca7d54-2c30-db11-9de9-000461428c89