Fix drag to add tiles showing too many times

It was appearing from the night tile being unavailable and causing
extra nulls in the list.  Fix the night mode tile so the nulls don't
happen.  Also fix the null handling to avoid this happening with other
bad specs.

Bug: 27061683
Change-Id: I48f769c06ed17c2ff1f166434857ec1faff14d02
4 files changed