Avoid overflow when calculating reverse indices#467

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michaelkirk-signal wants to merge 2 commits intoyapstudios:masterfrom

signalapp:mkirk/invalidFinalIndices

Commits on Aug 2, 2018

Fix overflow issue for invalid final indices.

charlesmchen-signal
authored and
michaelkirk
committed
Clarify finalIndices overflow changes, add asserts.
michaelkirk
committed