[FIX] web_editor: infinite loop in lists in table

Reproduction:
1. Open Notes App
2. Type text in two lines
3. Add a table
4. Select the first two lines and press backspace
5. Page will become unresponsive.

This is a backward port of: https://github.com/odoo/odoo/pull/126364



task-3504499

closes odoo/odoo#135486

Signed-off-by: David Monjoie (dmo) <dmo@odoo.com>