"issue" string not translated

Try http://www.softwaretesting.de/jira-demo/secure/Dashboard.jspa and let the mouse cursor hover over the red or green "open issues percentage diagram": the string "issues" is not translated, it should be "Vorgänge".

I believe I have translated all occurrences of "issues" in the properties files, maybe the issues string in the image alt tag it is not internationalized?