small "ü" in page as anchor causes a mistake when try to save (wrong JSON-response)

[gregordoehnert]

I tried to make some changes on a page with pre-block content. It contains some anchors and everytime I tried to save the page after some small changes I got the alert "Aktualisierung fehlgeschlagen. Die Antwort ist keine gültige JSON-Antwort.". The well know answer that there is something wrong with JSON.
I found the reason is that in the anchors where small "ü" (a german umlaut). It happened with the anchor target as well as with the anchor link. And at the same time there are some anchors with other umlauts, namely with a big "Ü", which do not cause the issue.