Several Minecraft mods enable the creation of multi-block ships. The
most common crafting recipe shared among them for a “steering wheel” or
“helm” node (they use different names for the equivalent of the meshnode
controller) is the following:
wooden plank, stick, wooden plank
stick, iron ingot, stick
wooden plank, stick, wooden plank
A good example would be Archimedes' Ships Mod:
http://www.9minecraft.net/archimedes-ships-mod/
I disabled some mods and a ship produces crash with error
```
2018-01-10 16:55:16: ERROR[Main]: ServerError: AsyncErr: ServerThread::run Lua: Runtime error from mod 'meshnode' in callback luaentity_Activate(): /usr/share/minetest/builtin/common/misc_helpers.lua:590: table index is nil
2018-01-10 16:55:16: ERROR[Main]: stack traceback:
2018-01-10 16:55:16: ERROR[Main]: /usr/share/minetest/builtin/common/misc_helpers.lua:590: in function 'copy'
2018-01-10 16:55:16: ERROR[Main]: .../games/whynot/mods/tools/meshnode/api.lua:40: in function 'get_tile_textures'
2018-01-10 16:55:16: ERROR[Main]: .../games/whynot/mods/tools/meshnode/api.lua:205: in function 'add_entity'
2018-01-10 16:55:16: ERROR[Main]: .../games/whynot/mods/tools/meshnode/init.lua:192: in function <.../games/whynot/mods/tools/meshnode/init.lua:160>
```
So this is a quick fix to get the world working again