When placing a station rail and submitting the formspec, the server
crashes with the following traceback:
2019-01-27 14:35:52: ERROR[Main]: ServerError: AsyncErr: ServerThread::run Lua: Runtime error from mod '' in callback on_playerReceiveFields(): ...st/mods/advtrains/advtrains_line_automation/stoprail.lua:86: attempt to index local 'stn' (a nil value)
2019-01-27 14:35:52: ERROR[Main]: stack traceback:
2019-01-27 14:35:52: ERROR[Main]: ...st/mods/advtrains/advtrains_line_automation/stoprail.lua:86: in function <...st/mods/advtrains/advtrains_line_automation/stoprail.lua:55>
2019-01-27 14:35:52: ERROR[Main]: /usr/share/games/minetest/builtin/game/register.lua:420: in function </usr/share/games/minetest/builtin/game/register.lua:400>