Step 4 of https://w3c.github.io/IndexedDB/#dom-idbobjectstore-createindex says:

If store has been deleted, throw an "InvalidStateError" DOMException.

We have a TODO for this step:

However, we have an implementation that can check this already:

Tests: ./mach test-wpt tests/wpt/tests/IndexedDB/idbobjectstore_createIndex.any.js (should have a new unexpected pass)