The mod Momentum (1.0.0) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event momentum::on_tick (ID 0)
Expected LuaEntity but non-object was provided.
stack traceback:
    [C]: in function 'damage'
    __momentum__/data/runtime/knockback.lua:75: in function 'handle_collidee_damage'
    __momentum__/data/runtime/knockback.lua:112: in function 'move_hittee'
    __momentum__/data/runtime/knockback.lua:150: in function <__momentum__/data/runtime/knockback.lua:135>

Oh interesting! I did not know non-objects could be collided with...

I can fix this but I'm also curious, do you know what you hit?