Fix mcq v4.2.0 migration throws on components without _items

[swashbuck]

Subject of the issue

The v4.1.0 > v4.2.0 migration throws a TypeError when a course contains an mcq component without an _items array. The mutate steps access MCQ._items.forEach(...) directly with no guard, so an itemless mcq crashes the whole migration (and any authoring-tool import that runs it). The bug is present on master (7.7.2).

Your environment

• Framework 5.56.2, adapt-contrib-mcq 7.7.2 (also present on master)
• N/A (build-time migration, not browser)

Steps to reproduce

1. Take a course with an mcq component that has no _items property.
2. Run the mcq migrations against it, e.g. grunt migration:test --file=adapt-contrib-mcq, or import the course into the authoring tool. (The migration's own testSuccessWhere already includes an itemless mcq: { _id: 'c-100', _component: 'mcq' }.)

Expected behaviour

An mcq with no _items should be handled gracefully (nothing to update) and the migration should pass.

Actual behaviour

The migration throws:

mutateContent -- MCQ - add item _isPartlyCorrect attribute TypeError: Cannot read properties of undefined (reading 'forEach')

In migrations/v4.js, the v4.1.0 > v4.2.0 block does MCQ._items.forEach(...) in the "add item _isPartlyCorrect" and "add item _score" mutates, and MCQ._items.every(...) in the matching checks, with no protection for a missing _items. (Other components such as accordion/hotgraphic use _items?.forEach(...).)

Suggested Fix (if known)

Guard _items in that block, e.g. MCQ._items?.forEach(...) in the mutates and (MCQ._items ?? []).every(...) in the checks.

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Posted via collaboration with Claude Code

[swashbuck]

See PR discussion.