Nested validation bug with version 3.6.0

**Describe the bug**
object or list widgets, that are nested inside parent object widget don't pass validation anymore.
Object has all fields optional, but is detected as required.
Empty list is detected as invalid. Adding and removing one item solves issue and empty list is then detected as valid.

**To Reproduce**
config.yml settings for fields:
```
{name: usefulInfo, label: useful info, widget: object, i18n: true, collapsed: true, summary: '{{fields.title}}', fields: [
{name: title, widget: string, i18n: true, required: false},
{name: text, widget: markdown, minimal: true, required: false, editor_components: []},
{name: button, widget: object, i18n: true, fields: [
{name: text, widget: string, i18n: true, required: false},
{name: href, widget: string, i18n: true, required: false},
]},
{name: linksTitle, label: links title, widget: string, i18n: true, required: false},
{name: links, widget: list, label_singular: link, i18n: true, fields: [{name: text, widget: string, i18n: true}, {name: href, widget: string, i18n: true}]},
]}
```
try saving entry with empty optional fields

**Expected behavior**
- object with optional fields should be valid if empty.
- empty list (of object that has required fields) should be valid

**Screenshots**

**Applicable Versions:**
- Decap CMS version: 3.6.0
- Browser version: Chrome

**CMS configuration**
```
backend:
name: test-repo

publish_mode: editorial_workflow
media_folder: assets/uploads
local_backend: true

collections:
- name: pages # a nested collection
label: Pages
label_singular: 'Page'
folder: _pages
create: true
nested: { depth: 100 }
fields: [
{name: usefulInfo, label: useful info, widget: object, i18n: true, collapsed: true, summary: '{{fields.title}}', fields: [
{name: title, widget: string, i18n: true, required: false},
{name: text, widget: markdown, minimal: true, required: false, editor_components: []},
{name: button, widget: object, i18n: true, fields: [
{name: text, widget: string, i18n: true, required: false},
{name: href, widget: string, i18n: true, required: false},
]},
{name: linksTitle, label: links title, widget: string, i18n: true, required: false},
{name: links, widget: list, label_singular: link, i18n: true, fields: [{name: text, widget: string, i18n: true}, {name: href, widget: string, i18n: true}]},
]}]

```

**Additional context**
could be caused by #7374