Requesting is not blocked when manual block expiration date is not set

Overview:
Request creation endpoint /circulation/requests ignores manual patron block if it does not have an expiration date.

Steps to Reproduce:
Reproducible only when called directly via API.
When trying to create a request via UI, manual blocks are checked preemptively and handled correctly by front end.

• block requesting manually for a user, but do not set block expiration date
• send a valid POST request to /circulation/requests

Expected Results:

• requesting fails, response contains a 422 error: "Patron blocked from requesting"

Actual Results:

• request is created successfully, manual patron block is ignored

Hint for dev:
UserManualBlocksValidator#isBlockedToCreateRequests