Before this commit, updating the color previews in the editor panel was
only done if the user remained in the "Theme" tab.

This means that those steps worked:

- Add a snippet in your page
- Go to the theme "tab"
- Change a theme color: validate the color you chose by closing the
  dropdown by clicking inside the theme panel, staying in the theme tab
- Click on the snippet
- Open the background option colorpicker -> theme colors are right

But those apparently same steps did not work:

- Add a snippet in your page
- Go to the theme "tab"
- Change a theme color: validate the color you chose by indirectly
  closing the dropdown by directly clicking on the snippet you added
- Open the background option colorpicker -> theme colors are wrong

task-3419142

closes odoo/odoo#128260

Signed-off-by: Quentin Smetz (qsm) <qsm@odoo.com>
Co-authored-by: utag-odoo <utag@odoo.com>