Code review comment for lp:~widelands-dev/widelands/bridges

I get an error when trying to load this savegame:
https://bugs.launchpad.net/widelands/+bug/734193/+attachment/5252593/+files/test_ferries_1.wgf

This savegame was made close before the other one. The difference is this savegame has no waterway yet. The other savegame has a waterway, which has no ferry: https://bugs.launchpad.net/widelands/+bug/734193/+attachment/5252594/+files/test_ferries.wgf