Survey actors for those that need to handle 'nil' values
With the addition of 'nil' values for tokens, there comes the question of how
existing actors response to 'nil' inputs. Does this create a problem? Does the
actor need to be rewritten to use the nil input?
This 'bug' is really a survey of how actors will respond to nils (ie actors
other than RExpession which is already set to handle such nils).