DS 1.5. Error when switching to plan mode

Hi!

I created a planning application in DS 1.5. with a crosstab with 5 new rows:

I use a button to toggle Input readyness.

Now, when there is already data to be displayed in the crosstab, everything works fine, I get 5 Input rows:

but when the crosstab is empty, meaning no records are to be displayed, and I toggle to Input ready, I get an error message:

It says Error when generating web item. the first error is Java.lang.IndexOutOfBoundsException:Index 6, Size:6 at Java.util.ArrayList.RangeCheck(ArrayList.Java:547) ....

I attached the exception chain as a text file.

I'd be glad if any of you could help me.

Kind regards, Thomas