Trying to add a new team member with a space at the back of the name will load indefinitely.

Summary

When trying to add a new team member by using the email address and having a space at the back, the dialog box loads indefinitely.

Steps to Reproduce:###

1. Access the User Groups page for a team account's settings: https://bitbucket.org/account/user/<team name>/groups/
2. Click on Add member
3. Input an email address to add a team member and put a space at the back of the name. Eg. "test@test.com "

Expected Results###

Either the user with the "test@test.com" email will be added or an error message will pop up and say the user is not found.

Actual Results

The spinner will spin indefinitely and the network console shows the following error:

#!html

15 Uncaught SyntaxError: Unexpected token < in JSON at position 0
    at Object.parse (<anonymous>)
    at r (add-member.js:41)
    at Object.<anonymous> (add-member.js:71)
    at c (jquery.js:3099)
    at Object.fireWith [as rejectWith] (jquery.js:3211)
    at n (jquery.js:8266)
    at XMLHttpRequest.<anonymous> (jquery.js:8605)
    at XMLHttpRequest.n (raven.js?ae06:314)
    at XMLHttpRequest.nrWrapper ((index):15)

Notes

The issue does not happen if you try to add a member with a username. Eg. "testuser111 "; It will fail and say the user is not found.