Validation fails when optional object field has required fields

I think this similar but not the same as #7383

**Describe the bug**

When an `object` field is optional but has a required field, it fails validation when all its fields are empty.

**To Reproduce**

Add this field to a collection:

```yaml
- name: submittedBy
label: Submitted by
widget: object
summary: '{{fields.name}}'
required: false
i18n: false
fields:
- name: name
label: Name
widget: string
- name: url
label: Url (separate multiple entries with a comma)
widget: list
required: false
```

Try to save an item without setting `submittedBy.name`

**Expected behavior**

Validation should pass, and item be saved without `subittedBy`

**Screenshots**

Instead:

**Applicable Versions:**

- Decap CMS version: 3.9.0