Assert that zerocoinDenomList is size 8.

Prevent any future development from forgetting to update the checkpointing process if the denom list changes.

src/accumulatormap.cpp

@@ -68,6 +68,9 @@ CBigNum AccumulatorMap::GetValue(CoinDenomination denom)
 uint256 AccumulatorMap::GetCheckpoint()
 {
     uint256 nCheckpoint;
+
+    //Prevent possible overflows from future changes to the list and forgetting to update this code
+    assert(zerocoinDenomList.size() == 8);
     for (auto& denom : zerocoinDenomList) {
         CBigNum bnValue = mapAccumulators.at(denom)->getValue();
         uint32_t nCheckSum = GetChecksum(bnValue);