At mentions are not displaying returned users

Summary

In certain situations it's possible for at mentions to return users from the REST endpoint, however the JavaScript does not present them as available users in the browser. As a result of this no users can appear as mentionable.

Steps to Reproduce

1. Setup users in a vanilla instance as follows:

       "name": "xcmvnx,mcnv",
       "emailAddress": "potato@example.com",
       "name": "asdkalkj",
       "emailAddress": "potato@example.com",
       "name": "a-train",
       "emailAddress": "potato@example.com",
       "name": "black noir",
       "emailAddress": "potato@example.com",
       "name": "gvbbvn",
       "emailAddress": "pxrzzkkcl@localdomain",
       "name": "hughie campbell",
       "emailAddress": "potato@example.com",
       "name": "jack from jupiter",
       "emailAddress": "potato@example.com",
       "name": "mister marathon",
       "emailAddress": "potato@example.com",
       "name": "queen maeve",
       "emailAddress": "potato@example.com",
       "name": "starlight",
       "emailAddress": "potato@example.com",
   

2. Try to at mention them using @p.

Expected Results

The users appear in the browser.

Actual Results

The REST endpoint returns these users, however they do not appear. As a result of this it looks like no users are returned.

Workaround

Given there is a max of 10 users returned, extending the search results using @pe or similar may return the actual users. If not, attempt to mention the user by changing the search results back-and-forth, for example if you wanted to mention a 'Joey':

1. Use @j
2. Then @p
3. Then @jo

Alternatively mentioning them by their name instead of email address will work, for example @mister marathon.