Adding a new array item should not also adding nested array item within it

[riceyeh]

Hi,
The following 2 tests show nested array items are added when adding an array item:

it('nested array item inside array item 1', () => {
const fields = [
'options',
'options[]',
'options[].oid',
'options[].amendments',
'options[].amendments[]',
'options[].amendments[].oid',
]
const $form = new Form({fields}, {name: 'form'})
const $option = $form.$('options').add()
$option.update({oid: 1})
expect($form.select('options.0', null, false)).not.to.be.undefined
expect($form.select('options.0.amendments.0', null, false)).to.be.undefined // <--- fail
})

it('nested array item inside array item 2', () => {
const fields = [
'a',
'a[]',
'a[].oid',
'a[].b.c',
'a[].b.c[]',
'a[].b.c[].oid'
]
const $form = new Form({fields}, {name: 'form'})
const $a = $form.$('a').add()
$a.update({oid: 1})
expect($form.select('a.0', null, false)).not.to.be.undefined
expect($form.select('a.0.b', null, false)).not.to.be.undefined
expect($form.select('a.0.b.c', null, false)).not.to.be.undefined
expect($form.select('a.0.b.c.0', null, false)).to.be.undefined // <--- fail
})