Help with Crystal formula

I managed to resolve my previous thread partialy wit one small problem

{items.qty} & ", " & {items.name} & ", "& {item.subname} & ", " & "Net kg: " & {items.mass}

This prints

5, Printers, HP Deskjet, Net kg: 5

Prints OH but if a database field eg {item.subname} is empty then the line does not print

I have tried

if {item.subname} = "" then {item.subname} = "-"
{items.qty} & ", " & {items.name} & ", "& {item.subname} & ", " & "Net kg: " & {items.mass}

this however gives an error message 'The remaining text does not apear to be part of the formula'

I then tried

if {item.subname} = "" then {item.subname} = "-";
{items.qty} & ", " & {items.name} & ", "& {item.subname} & ", " & "Net kg: " & {items.mass}

with the same result the line does not print prints

The trouble is the datafield is null and the formula does not know how to handle it. You can solve this in a couple of ways
1) Go into File/Report Options and check Convert Database NULL Values to Default. This will affect the entire report (fields), treating null values as empty strings, but your original formula will now work for each.
2) Instead of a formula, use a text object. Drag an empty text object onto your form, then drag each field into it and add commas in between each. The text object resolves null fields for you and treats them as empty strings.
3) In your formula you need to use an isnull() function on fields that may result in nulls, all while appending to create one big string.