Bug 314382

When all org-iso-mdoc credential requests fail protocol-specific validation in the IdentityDocumentServices framework, CredentialRequestCoordinator::prepareCredentialRequest() proceeds to show the credential picker with an empty request data set, instead of rejecting the promise with a TypeError as required by the spec. Steps to reproduce: 1. A website calls navigator.credentials.get() with one or more org-iso-mdoc requests 2. ALL requests contain malformed deviceRequest or encryptionInfo data that fails framework validation 3. The IdentityDocumentWebPresentmentRawRequestValidator rejects each request (console warnings are logged) 4. DigitalCredentials::validateRequests() returns an empty vector (no exception) Expected: The promise should be rejected with a TypeError, matching the spec's "Prepare credential requests" algorithm step 7: "If validatedRequests is empty, reject the credential request with a newly created TypeError." Actual: The empty vector is passed to DigitalCredentialsRequestDataBuilder::build(), which wraps it in a DigitalCredentialsRequestData struct, then showDigitalCredentialsPicker() is called with empty request data. Fix: Insert isEmpty() check after releaseReturnValue() and before setCurrentPromise() in CredentialRequestCoordinator::prepareCredentialRequest(). Spec reference: https://w3c-fedid.github.io/digital-credentials/#prepare-credential-requests (step 7) rdar://176530716