"Search users" in Assignee list broken and returns no results
### Summary
When assigning a bug, there's a dropdown for Assignees, along with a search box which filters the available list. It doesn't work at all.
### Steps to reproduce

Now let's press "a" or "s":


### What is the current *bug* behavior?
Search filtering is hosed.
### What is the expected *correct* behavior?
Search filtering works as expected.
issue