Dragging a story with more than 12 subtasks to a new version in the Planning Board fails

1. create a story with more than 12 subtasks
2. in the Planning Board, drag the story to a new version

Observed:
The Update Version popup is broken. None of the cards show for the subtasks on either page. Once you click Update, none of the subtasks are moved, even if you make sure to click the Select All option.

Expected:
Dragging a story with more than 12 subtasks should work the same as one with fewer subtasks.