* Before the Email/Exchange split, EmailProvider was guaranteed not to return a null
cursor; this is no longer true
* We now throw a new RuntimeException (ProviderUnavailableException) when calling
commonly-used utility methods (e.g. restoreXWithId) and the cursor as returned from
EmailProvider is null (which implies that the provider isn't available).
Change-Id: I152d13bff0129c23586cd570d23c87d69cfce372
74143e89d5