Search suggestions for the "Subgroups to Add" field show a missing translation when writing the name of a group that doesn't exist

Steps to reproduce:

• Login as an admin
• Hover over "Wiki" and click on "Administer Wiki"
• Click on "Groups"
• Click on the small yellow pencil to the right of the group you want to edit (in my case XWikiAdminGroup)
• Start typing the group's name in the "Subgroups to add" input field
  • If the group exists a suggestion will be displayed (subgroup.png)
  • If the group doesn't exist the suggest shows: "core.widgets.groupPicker.noResults" (subgroup2.png)

If you try the same scenario for the "Users to Add" field you don't get that message (user.png).

Tested on Chrome 23, Firefox 17 and IE9.