Drilling down into NULL

Dear fellow Power BI enthusiast,

I have trouble with a drill-down hierarchy and looking for any type of workarounds/solutions. The hierarchy consist for 7 levels. For example: http://imgur.com/a/GOsxy

If someone of level 1 is drilling down and that is the only level that exists (Picture - Row 4), it will be possible to drill down through 6 instances of NULL. Not so beautiful! 

I have not found any functionality for disabling drill-down if null or similar.  A potential solution could be to replace null with last value. Row 4 would be covered in "J" and row 3 would have Level 3 - 7 covered with "I". The solution is not so functional as it would be confusing to know where in the drill-down you are, as alot of levels look the same.

Looking for any type of tips for handeling this. 

Best regards,

Christofer