Creating user fails when abbrevation is shorter than 3 characters

[cweiske]

.. but no error message is shown.
Browser console shows:

TypeError: b is nullext-all.js:21:511004
    removeCls ExtJS
    showNotification http://tt.sybo/bundles/netresearchtimetracker/js/main.js:323
    failure ../bundles/netresearchtimetracker/js/netresearch/widget/Admin.js:1064
    ExtJS 4
        callback
        onComplete
        onStateChange
        bind