code: public static Object toNull(Object value) throws PageException {
  	if (value == null) return null;
  	if (value instanceof String && Caster.toString(value).trim().length() == 0) return null;
  	if (value instanceof Number && ((Number) value).intValue() == 0) return null;
  	throw new CasterException(value, "null");
      }
docs: casts a Object to null
  
  @param value
  @return to null from Object
  @throws PageException