Whenever I try to generate a structure that has a spawn script that uses a structure list, the game crashes. Furthermore, after experiencing this crash, my game for some reason thinks that save that crashed is a multiplayer server. Whenever I try to open that save it gives a "Disconnected from server" error and kicks me to the multiplayer section of the main menu.

Crash report attached
Crash.txt

Are you on the latest version? Because I think that's been fixed in 1.2.10.

I'm using 1.2.10 for Minecraft 1.10. But I'm also testing this with structures I made with an older version of Recurrent Complex, would that be a problem?

Nope, ReC should be 100% backwards compatible (and afaik no version of the structure files should be broken). I'll investigate then.

Not sure how this would even happen but I think it shouldn't happen again. If it reoccurs in the next version (probably 1.2.10.1) please reopen the issue.