How to pull report entries when one column is blank for certain rows?

Summary:

I'm building a report showing certain incidents, and I'd like to include the most recent thread entry in the report. The challenge is, I have many incidents without thread entries and those do not show on the report.

I tried if(length(treads.notes)>0, thread.notes, "no notes"), but only items with notes return in the report.

How do you add a column that can be blank?