elfeed-db-load: Wrong type argument: avl-tree-, nil with Emacs 29.3 and no upgrade

[al3xandru]

By searching old issues, I have found similar issues (listed below).
The majority of these are not marked as solved and they refer to upgrading Emacs versions. The latter condition does not apply in this case at all: I'm using Emacs 29.3 on macOS.

The errror is the one in the subject: elfeed-db-load: Wrong type argument: avl-tree-, nil

Possibly related issues:

• #340
• #466
• #284

[al3xandru]

Every usage of elfeed results in this error next try I try to load it.

I tried:

1. use elfeed-search-quit-window
2. use elfeed-search-quit-window followed by elfeed-db-unload
3. use elfeed-db-unload
4. not doing anything

In all these cases the next invocation of elfeed results in this error.

[al3xandru]

I have compared index and index.backup: the files are identical. I assume elfeed reports an error simply by checking there's an index.backup file?

[al3xandru]

I am using the patch described in this comment https://github.com/skeeto/elfeed/issues/466#issuecomment-1275327427 and I haven't seen the issue since. I believe this would indicate this is a bug. I don't know how to fix this in elfeed and I see no activity on the project.