Fix #2267475 (NPE when changing incoming settings for EAS)

* When settings are changed, we loop through the sync error map,
  clearing mailboxes in the changed account that are in an error
  state.
* It's possible that there are mailboxes referenced in the map that
  no longer exist.  When trying to retrieve them from the provider,
  null is returned, but we're not checking for this case, and an
  NPE results.
* The fix is simply to check for null, and clear the error map for
  the mailboxId that references a deleted mailbox

Change-Id: I8c1c847090026fa1c53b09bbe6b12d864bce4df1
1 file changed