Hi all

I have a list column, that includes nulls, like this:
ExpandListWithNull1.png

When I try to extract the values, I get errors on all the nulls:
ExpandListWithNull2.png

ExpandListWithNull3.png

The code for this step is this:
= Table.TransformColumns(#"Filtered Rows", {"departmentNumber", each Text.Combine(List.Transform(_, Text.From), ","), type text})
I tried including something like this, in the step, but without success:
each if [departmentNumber] = null then null else
How can I avoid these errors when I extract values?

PS: I would very much have liked to attach a sample sheet, but these list columns (I have a lot of them) are derived from a large dataset, which includes sensitive data, and Im not really sure how to make such a column from scratch.

Best regards
Imbizile