[bug] drillthough with hierarchy not displaying values

Hello,

I am using a custom API source and there seems to be a bug when I open the drillthrough and select a hierarchy value, it doesn't display the values.  It works fine when I have the hierarchy selected in the pivot before opening the drillthrough.  But if I don't have the hierarchy selected in the pivot and open the drillthrough and add it as a value, it returns nothing.

I was able to recreate it with a demo from flexmonster https://jsfiddle.net/flexmonster/o4jywt38/.  Here is an example.

Looking at the API calls it makes it looks like when the hierarchy is part of the pivot, it requests the correct fields in the drillthrough, but when it is not part of the pivot, in the drillthrough it sends the hierarchy name as a field which is causing the error.