Difference in dimensional expressions between RS8.2 and 8.3 - part two

I found another one

code in 8.2

set( emptySet([My Dimension].[My Hierarchy]) )

code in 8.3

set( item(emptySet([My Dimension].[My Hierarchy]),0) )

without the use of item() you get an error
Invalid coercion from 'memberSet' to 'member, measure'
even though the expression validates.

This is important when you want to create prompts that return MUNs but are optional.
As a recap from my older posts optional for a prompt means that it has a default value. The default is ... no members selected
...in other words: empty set