Remove call to addError, as it isn't defined anywhere

[cainux]

I'm coming across schema which look something like:

protocol x {
  @namespace("foo")
  fixed Code(3);

  record Currency {
    @java-class("java.math.BigDecimal") string amount;
    foo.Code code;
  }
}

So RecordConverter ends up calling addError before returning "any", which doesn't seem to have a body defined anywhere, resulting in an error.

This PR is a small change to sidestep the error.