[FIX] web_editor: Focus on composer if no anchor selected

Steps to reproduce:

  - Go to any chatter
  - Click on "Send message"
  - Open the Full Composer
  - Click directly on the "Link" button of the composer
  - Add label and url then save

Issue:

  Link not added to composer.

Solution:

  Restore the "old range" only when selection is cancelled by focus.

Related fixes:
https://github.com/odoo/odoo/commit/da14e4449e5e318eb72e1b9f268fb797adb0c6a6
https://github.com/odoo/odoo/commit/d2f3c9e7975188753fa17c06db3fc5c73c773944



opw-2544149

closes odoo/odoo#78583

Signed-off-by: Nasreddin Boulif (bon) <bon@odoo.com>