"Clear deleted" on a many tickes could result in "list index out of range"

[runborg]

Version: 0.9.20

When clearing out a lot of closed tickets with the "Y" command, the code could fail with a list index out of range.

  File "/home/runarb/.local/bin/curitz", line 8, in <module>
    sys.exit(main())
  File "/home/runarb/.local/pipx/venvs/curitz/lib/python3.10/site-packages/curitz/cli.py", line 1182, in main
    curses.wrapper(uiloop, config)
  File "/usr/lib/python3.10/curses/__init__.py", line 94, in wrapper
    return func(stdscr, *args, **kwds)
  File "/home/runarb/.local/pipx/venvs/curitz/lib/python3.10/site-packages/curitz/cli.py", line 404, in uiloop
    runner(screen, config)
  File "/home/runarb/.local/pipx/venvs/curitz/lib/python3.10/site-packages/curitz/cli.py", line 866, in runner
    lb.draw()
  File "/home/runarb/.local/pipx/venvs/curitz/lib/python3.10/site-packages/curitz/culistbox.py", line 69, in draw
    if isinstance(self.elements[i], BoxElement):
IndexError: list index out of range```

This might because of the current "page" of tickets is beeing deleted, or something like that. 
I've not debugged the issue other than found it happening when cleaning a lot of tickets when debugging zino2

[runborg]

It looks like the issue is with the current "page" not existing after the delete operation completes. if the cursor is on a page beeing deleted after the removal operation it will give this error. if the cursor is on a page not deleted it works as expected.