Long usernames run into the "inner frame"

Hi,

I just realised that if you edit a user with a long username (because
it’s an email address), the username will be written beyond the left
tab into the “main” “frame” of the page.

Maybe just cut of the username when it reaches beyond the left tab?
Word-wrapping it doesn’t make much sense IMO, as it’s written out in
full on the top of the page anyway.

Rainer