Crash on save game load

Issue description

I was designing a stacker onto an existing track. An odd piece of yellow track appeared on the existing track which stopped the running trains. The direction, exclusion, and no-stop tools were acting weird, not working, so I saved the game and exited to the main menu. Then I tried to load that save.

Reproduction steps

Load attached save. Will crash.

Github won't accept my 32MB save file, and your save game files are already compressed, so here it is on my Google Drive as Temp.save:

https://drive.google.com/file/d/12zMC8o3X1pBRBVKRtMap4uaFI1smg6v7/view?usp=sharing

I can be reached by email: Tergiver at msn.com.

Game version and build number

v0.7.7 b470

Operating system

Windows

Thank you for the save fle. But it would help here even more to know how you managed to get into that state. Also we made several fixes in the train graph over last few weeks. Are you still able to reproduce this issue (ignoring the already broken save file)?

We found a case where this corruption can occur and fixed it. We hope that was it, but one can never rule out another possibility If this happens again, please file another issue so we can investigate more.