Failed to forget recent connections

[playgithub]

Problem

When click "Forget Recent Connections" in the context menu of the taskbar item, as in the screenshot above, it just do nothing.

Reproduce

1. In goldendict-ng / Edit / Dictionaries / Sources / Websites, add a dict, whose address is "https://dict.youdao.com/search?q=%GDWORD%&ue=utf8", whose name could be arbitrary (e.g. YouDao), and enable it.
2. Search "Hello", in the result from the dictionary just added, click any link, it will be opened in ungoogled-chromium
3. The link will be added to recent connections, as in the screenshot above
4. The added connection can't be delete by click "Forget Recent Connections"

[playgithub]

Not a problem of chromium, solved by tries as below:

1. delete "~/.local/share/recently-used.xbel", it contain the connections, but it doesn't solve the problem
2. delete everything in ".local/share/kactivitymanagerd/resources", and reboot, the problem is solved

BTW, not sure if step 2 solves the problem without step 1.