on the latest releases, a new feature called: table column visibility condition is available, you can use it to hide your column expression where it is null, using this:
=len(trim(measure2))<>0
but I don't think you can do this on a pivot table..
This new feature is fantastic, however, when I tried to export the report with hidden columns, I got an error message "Internal engine error". Have you gone through this issue as well?
PS.: This feature only works with straight tables.
