Since [1] dropped images are saved as attachments. When such an image is a WEBP, its pre-computed resizes and conversions to jpeg are not generated. This commit adds the behavior of saving an `o_modified_image_to_save` when a `o_b64_image_to_save` is a WEBP. [1]: https://github.com/odoo/odoo/commit/3bbce756c69a206d07abd31059f0392c26b36096 task-2774352 Part-of: odoo/odoo#85494