Throw IAE when service add null AutofillIds on SaveInfo methods.

Test: existing CtsAutoFillServiceTestCases pass
Test: manual verification using Contacts app
Test: manual verification adding a CTS test case that crashes the app, but such
      test cannot be commit because once the issue is fixed, it crashes the
      service (the right way to test this fix is through unit tests against
      exceptional conditions, but we don't support those on Autofill yet).

Fixes: 62649290

Change-Id: I8fc01fa929270219cd40035ff02eaf0dda5ecbfa