Do not attempt to configure null preferred activity

On non-phone devices the default SMS app is null. During the set/get paths
we would not try to configure the activity, but during the package update
path we called 'getDefaultSendToApplication" and configured it without
validating that it is non-null. This change adds the null check.

Bug: 11482259 When default SMS app changes we need to update the default app for the SEND intent
Change-Id: I227cfd803fd0667d78918a720b5a6eae9d57ea9d