Book editor crashes when adding new entry in ToC editor

[Urnoev]

calibre 7.20
Linux (openSUSE Tumbleweed (6.11.3-2-default))

When editing an epub file in the book editor and creating a ToC using the ToC editor ("Edit Table of Contents"), after generating the ToC via "Generate ToC from major headings", trying to add additional entries via the "New entry inside/above/below this entry" buttons causes the editor to crash:
The ToC editor closes without an error message and the book editor becomes unresponsive. The book editor process has to be killed manually.

[Kovid Goyal (kovid)]

This is a Wayland issue. Switch to X11 or just run calibre under
XWayland via QT_QPA_PLATFORM=xcb and you will be fine.

[Urnoev (urnoev)]

I am not using Wayland, my system runs with x11:

# loginctl show-session 3 -p Type
Type=x11

[Kovid Goyal (kovid)]

Fixed in branch master. The fix will be in the next release. calibre is usually released every alternate Friday.