Alpine wire entangle causes "Uncaught (in promise) TypeError: Cannot read properties of null"

I'm using a custom form component, based on Textarea.

As soon as I put this in:

x-data="{ state: $wire.entangle('{{ $getStatePath() }}').defer }"

x-data="{ state: $wire.entangle('{{ $getStatePath() }}').defer }"

x-data="{ state: $wire.entangle('{{ $getStatePath() }}').defer }"

x-data="{ state: $wire.entangle('{{ $getStatePath() }}').defer }"

and I click a button on the page, I get:

Uncaught (in promise) TypeError: Cannot read properties of null (reading 'child_description')
    at livewire.js?id=90730a3b0e7144480175:14:130978

Uncaught (in promise) TypeError: Cannot read properties of null (reading 'child_description')
    at livewire.js?id=90730a3b0e7144480175:14:130978

Uncaught (in promise) TypeError: Cannot read properties of null (reading 'child_description')
    at livewire.js?id=90730a3b0e7144480175:14:130978

Uncaught (in promise) TypeError: Cannot read properties of null (reading 'child_description')
    at livewire.js?id=90730a3b0e7144480175:14:130978

That "child_description" is inside a JSON field:

Textarea::make('viewpoint.child_description')

Textarea::make('viewpoint.child_description')

Textarea::make('viewpoint.child_description')

Textarea::make('viewpoint.child_description')

When the field has a value, the error is gone. But initially, the JSON is null. (empty string doesn't solve the problem)

Any idea how to solve this?