Fix TextClassifier logging.

No logs were being sent via the TextClassificationManagerService to
the TextClassifierService.
Also, SelectionEvent.getSessionId() is nullable. Handle appropriately.

Bug: 79418429
Test: manual - manually tested via a debugger. Auto tests coming soon.
Test: bit CtsViewTestCases:android.view.textclassifier.cts.TextClassificationManagerTest
Change-Id: I196885d9b03c0c11cae7686a5835d14791065e78