A username with space(s) cannot view his/her activity on the User's profile

If a username contains space(s) (Ie. JIRA Admin), then the activity stream on the User's Profile will not work properly

Steps to replicate:

1. Create a user with spaces (Ie. JIRA Admin)
2. Perform any actions on any issue (Ie. Start Progress, Resolved, and etc)
3. The above action should be displayed on the Profile's Activitiy Stream, but it does not
   • Either the Profile's Activity Stream shows no activity or
   • Show another user activity with the same username's prefix (In this case, JIRA)

Note: The activity will show as normal on the activity stream's gadget.