Theoretically got the segfaults due to the enemies to stop by
initializing any unitialized chunks.  I don't know why the chunk_map
not being large enough hasn't been an issue, but it doesn't seem to
cause any problems for some reason.  I think that maybe the way it's
set up, they can go out of scope in the negative direction without
being deleted, but if they go out of scope in the positive direction,
they're immediately removed.  This is just a guess, but it seems to
be running fine now.  And since the negative direction will always
be within the size of the chunk_map, it's not an issue.