Fix withItemData treating sessions that don't match an item as valid

[emmatown]

To test this, start one of the examples with a new database, create a user then restart the example with a new database and go the admin ui again and you should be prompted to create a new user rather than be logged in

[changeset-bot]

🦋 Changeset detected

Latest commit: 5c099df

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 12 packages

Name	Type
@keystone-next/keystone	Major
@keystone-next/test-utils-legacy	Patch
@keystone-next/benchmarks-legacy	Patch
@keystone-next/example-auth	Patch
@keystone-next/app-basic	Patch
@keystone-next/example-ecommerce	Patch
keystone-next-app	Patch
@keystone-next/example-roles	Patch
@keystone-next/example-sandbox	Patch
@keystone-next/example-todo	Patch
@keystone-next/admin-ui	Patch
@keystone-next/auth	Major

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[emmatown]

Note this case never happened because findOne throws when it doesn't find an item

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[timleslie]

👍