[FIX] GrowingList: Fixed issue with partial responses (serverside paging)

If getContexts() does return some data but also triggers a new request to the
service, the list must be updated accordingly. Only if an empty diff is
contained (so no new entries are available yet) the update can be skipped.

Change-Id: Ic4e7501d5b47bd801ea5f6a8081a20573d6db683
Merge "[FIX] GrowingList: Fixed issue with partial responses (serverside paging)"