Manually deleting buffers breaks the marks list

[alek3y]

Steps to reproduce:

1. nvim A B
2. :bd on A
3. Open the quick menu
4. Write down A and press Enter

From some debugging I found the flow of the program during the last step to be:

1. on_menu_save is called to update the marks (likely inside toggle_quick_menu because of the BufLeave event)
2. Inside of it set_mark_list runs vim.fn.bufnr("A") which returns 1 instead of -1 despite not being on the list
3. update_buffers is called which doesn't delete nor bdadds the A buffer back (because bufnr is not -1)
4. select_menu_item starts nav_file which runs update_marks
5. Inside of it remove_mark(1) is executed because buffer_is_valid returns false (since vim.fn.buflisted(1) returns 0 because it wasn't bdadded) which effectively undos the last step

This problem could be avoided by simply using :bw instead of :bd, as the help page mention it doesn't completely delete the buffer, however I think there should be a way to detect if the buffer is nobuflisted (which seems to be the option set on the buffer after :bd).

This was a little hard to dig out so I hope I got everything right.

[j-morano]

Hello. Thank you very much for the feedback, and for doing most of the work by debugging the code. I added a commit that fixes this issue. However, please check if it is working as intended, and feel free if to reopen it if it is not.

[alek3y]

Yes, it seems to work as expected. Thanks!