Intro breaks after selecting tracker

[slabstone]

I made a simple intro with 3 steps, #issue_tracker_id, #issue_subject and #issue_description. If I try to change the tracker while intro is active, it minimizes into top right corner, then the screen remains darkened and nothing happens. Typing subject and description works fine.
Tested with Redmine 3.3.1 and 77ff085.