fix: model cleanup not working with nested schemas (fix #227)

[victorlambert]

Fix #227
What kind of change does this PR introduce? (check at least one)

• Bugfix
• Feature
• Code style update
• Refactor
• Build-related changes
• Other, please describe:

Does this PR introduce a breaking change? (check one)

• Yes
• No

If yes, please describe the impact and migration path for existing applications:

The PR fulfills these requirements:

• When resolving a specific issue, it's referenced in the PR's title (e.g. fix #xxx[,#xxx], where "xxx" is the issue number)
• All tests are passing: https://github.com/formvuelate/formvuelate/blob/main/.github/CONTRIBUTING.md#development-setup
• New/updated tests are included

Other information:

[logaretm]

Thank you! This looks good but can we make this a little bit tighter by adding a test for it?

The test should fail before you've applied your fix and should pass afterwards. You can take a look at similar tests in the packages/formvuelate/tests/unit/SchemaForm.spec.js.

Something similar to this test here:

https://github.com/formvuelate/formvuelate/blob/main/packages/formvuelate/tests/unit/SchemaForm.spec.js#L528

[victorlambert]

Here you go, thanks for this great package !

[logaretm]

LGTM

[marina-mosti]

Thanks for the PR @victorlambert looks good