NOTE: Only be using Crystal for a few days so hope this helps ...

I tried the Concatenation with + and found odd results coming back akin to issues I'd seen with MySQL concat vs. concat_ws

The answer I came up with was:

{fn CONCAT({fn IFNULL(`tblperson1`.`SurName`, '')}, ', ',{fn IFNULL(`tblperson1`.`FirstName`, '')}, '. ' , {fn IFNULL(`tblperson1`.`MIddleName`, '')})}

So it puts a blank if a null field but outputs:
Surname, Firstname. Middlename
or at least the value's within those fields.

I could be making it more complicated or I've missed something but the answer I came up with at least works for me