Fix NPE when ranking update causes reinflation

Pass in the NEM inflation callback to RowBinderImpl's
onNotificationRankingUpdated since changes in state in ranking can
trigger inflation (smart replies and conversations)

Also go ahead and support null callbacks in inflateContentViews.

Bug: 154028814
Test: build
Change-Id: I265e2a9e6b707bd908ce8c1ae5957cfe76973a5f