When restoring a checkpoint, I receive a strange error:

STARTUP ERROR:
An exception was generated upon starting up from a checkpoint.

java.io.InvalidClassException: brain.BrainHelper; brain.BrainHelper; no
valid constructor

This class BrainHelper is only used as a helper class to evaluate the
individual, and is not referenced by EvolutionState, the problem, or the
Individual. I could create a default constructor that does nothing, but I am
curious why this class is even relevant?

Thanks for any help.