I just tried to launch my first rocket and the game crashed with this error:

32274.530 Error MainLoop.cpp:1205: Exception at tick 18877470: The mod Warptorio2 Expansion (0.18.57) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event warptorio2_expansion::on_rocket_launched (ID 10)
warptorio2_expansion/control.lua:1315: attempt to index field 'enemy-base' (a nil value)
stack traceback:
warptorio2_expansion/control.lua:1315: in function 'CallFrenzyAttack'
warptorio2_expansion/control.lua:2941: in function <warptorio2_expansion/control.lua:2938>

I am on the newest version of Warptorio(1.2.8) and Warptorio2 Expansion (0.18.57) and have no big overhaul mods installed.

I launched my rocket from an Ocean Planet, maybe the fact that there are no biters is causing it?

Probably caused by the my function that is calling biters. I will have to fix it on the next version. Thanks for the report

Thanks for the quick fix.

I haven't played the expansion version of Warptorio 2 but it simply looks to me that the rocket was launched on a different level than the surface level. It's calling for an enemy base but they will simply not exist on any level other than surface.

I bet if you would fix it, you could still break the frenzy attack/boss spawn simply by removing your last silo in the moment you launch the rocket.

I would suggest changing the object from silo to the warp reactor, either that or an if/else statement in case someone is witty enough to remove the silo on_rocket_launched. As far as I know, on_rocket_launched doesn't trigger until it's already way up in the air.