Increment witnesses for new transactions on rescan

Closes #1400

src/main.cpp

@@ -2079,6 +2079,8 @@ bool ConnectBlock(const CBlock& block, CValidationState& state, CBlockIndex* pin
     // Construct the incremental merkle tree at the current
     // block position,
     auto old_tree_root = view.GetBestAnchor();
+    // saving the top anchor in the block index as we go.
+    pindex->hashAnchor = old_tree_root;
     ZCIncrementalMerkleTree tree;
     // This should never fail: we should always be able to get the root
     // that is on the tip of our chain