Handle empty tag for EAS 14 event reminder

* EAS < 14 doesn't send a tag when there's no reminder; EAS 14
  sends an empty tag, which we interpret as 0 minutes
* Fix is to detect the empty tag and not create a reminder in this
  case

Bug: 5848662
Change-Id: Id7a8e1d4b4c72e1456e15a1a209cbf60586f9f84
2 files changed