Check for null string

Check for null string to avoid null pointer exception when checking for end of string. If string is null, immediately return at-end condition.

Signed-off-by: Herb Bowie <hbowie@mac.com>
Broadened Exclusion Criteria for Sequence Value of 4

In order to be assigned a sequence value of '4', indicating an event that has already occurred, the event must have a complete date occurring on or before today, and must not have a status of 'future', 'discards', 'ideas' or 'next year'.

Signed-off-by: Herb Bowie <hbowie@mac.com>