**Problem**:

When editing the subtasks of a project task, in mobile version (kanban view), closing subtask view triggers reloading of the task's subtasks (before the update). This causes the changes to be overwritten. This issue only happens in incognito mode mobile version when debug mode is not enabled. It also affects some databases that have customized views before upgrading to 18.0 (see the ticket 4499150)

**Details**
This issue was introduced after removing the sequence field from the kanban view in this pr https://github.com/odoo/odoo/pull/174671/commits/75c9b74488f9b49b70b2949ecb5277e57024f468 The PR removed the sequence field from the kanban view of project.task, causing the sequence field not to be loaded into the child_ids of the main task. This triggers the loading of child tasks when there is a mismatch between the field names and the loaded field names of child_ids in the relevant function https://github.com/odoo/odoo/blob/18.0/addons/web/static/src/model/relational_model/static_list.js#L857-L872.

- How to reproduce:
    * Open incognito mode mobile version
    * Refresh the page
    * go to a project task that has a subtask
    * edit the subtask and try to save

See the following video: https://drive.google.com/file/d/1QT7AxgDM1DLTfm-KWhfF3IdsU4h8WpYA/view?usp=sharing

**Solution**:
Add sequence field back to the task kanban view.

opw-4499150

Description of the issue/feature this PR addresses:

Current behavior before PR:

Desired behavior after PR is merged:




---
I confirm I have signed the CLA and read the PR guidelines at www.odoo.com/submit-pr

**Steps to reproduce:**
- Install Accounting
- On Accounting dashboard, click on "Import File" button of Bank journal
- Select a CSV file with bank statements
- On the left menu, select "No Separator" as "Thousands Separator"

**Issue:**
"Comma" is displayed as selected instead the first time.
The second time "No Separator" stays as selected.
However, the value sent when testing or importing is not the correct one.

**Cause:**
"No Separator" option should have an empty string as value.
However, during the generation of the "select" element, the value for the "option" element is evaluated with:
`opt.value or opt`
As `opt.value` is the empty string (evaluated to False), `opt` is used instead, even if it is an object, which is not correct.
The main issue is that the empty string is not handled as a valid value.

**Solution:**
Handle the empty string as an acceptable value.

opw-4325310




---
I confirm I have signed the CLA and read the PR guidelines at www.odoo.com/submit-pr

Forward-Port-Of: odoo/odoo#192536