Check_mk und Cacti+Weathermap

After i added the first traffic line i am getting an error that makes the map unusable anymore:
Javascript error occured: TypeError: output.match(…) is null /check_mk/nagvis/frontend/nagvis-js/js/NagVisCompressed.js?v=1.9.20 (3578)

In the top it keep saying “Loading…” and the traffic line is not shown.

Anything i am doing wrong here?