[r8663] "Withdraw all" segmentation fault

[captain crunch]

Simutrans 120.4.1 Nightly released Feb  2 2019 on Linux amd64.
Pressing "Withdraw all" button in line management window crashes the program.
To reproduce load the attached saved game, open the line management window, select "(1) Line" and press the "Withdraw all" button.

[Dwachs]

Thanks for the report. I tried to fix this in r8667. But I am not sure whether I found all crashing code paths.