Copy/paste of objects in array fields does not work with anonymous objects

[stianmartinsen]

Describe the bug

Copying and pasting array items (introduced in Sanity v3.54.0 in pull request #7292) requires the objects to have a name. If not provided, the error "Value of type "object" is not allowed in this array field" appears on the screen.

To Reproduce

This is an example of a simple schema that has an "Accordion" field. This is an array with anonymous objects.

import {defineType, defineField, defineArrayMember} from 'sanity'

export const page = defineType({
  type: 'document',
  name: 'page',
  fields: [
    defineField({
      type: 'string',
      name: 'title',
    }),
    defineField({
      type: 'slug',
      name: 'slug',
      options: {
        source: 'title',
        maxLength: 96,
      },
    }),
    defineField({
      type: 'array',
      name: 'accordion',
      title: 'Accordion',
      of: [
        defineArrayMember({
          type: 'object',
          fields: [
            defineField({
              type: 'string',
              name: 'title',
            }),
            defineField({
              type: 'text',
              name: 'content',
            }),
          ],
        }),
      ],
    }),
  ],
})

To replicate the issue, try to open this in the Sanity studio, create a page with an accordion array item, and lastly try to copy/paste the row.

Expected behavior

Because naming your objects in array fields isn't mandatory (if you don't have multiple objects available in the same array field), I would expect copy/pasting anonymous objects in array fields to work.

Screenshots

This is the error message I get when trying to copy and paste an accordion item:

Which versions of Sanity are you using?

@sanity/eslint-config-studio   4.0.0 (up to date)
@sanity/vision                3.60.0 (up to date)
sanity                        3.60.0 (up to date)