Python crashed when calling env.get_state() with use_generated_assets set to True

[Kaixin WANG]

To reproduce:

from procgen import ProcgenGym3Env

env = ProcgenGym3Env(
    num=1,
    env_name="bossfight",
    use_generated_assets=True
)

rew, obs, first = env.observe()
state = env.get_state()

[Kaixin WANG]

I found the cause https://github.com/openai/procgen/blob/master/procgen/src/basic-abstract-game.cpp#L1238