Pivot used to have a column label (blank), now just displays a less-than date field

Several months ago, when grouping a pivot table by date (year), there would be a column labeled, "(blank)" that tallied all records that did not have a date listed.

Now, that shows a date - e.g. "<8/31/2018" instead of "(blank)"

Not sure when it changed, but is it possible to force the label to blank instead of a less-than date?

Thanks for the reply. I guess the issue is that, several months ago, it automatically labeled that column as (blank), even grouping a date field. Somewhere in the past few months, that behavior has changed to now just show the less-than date... Wondering if there's a way to revert to showing that as blank without me manually typing in that cell each time.