Sync hashchain bug fixed

src/wallet/wallet2.cpp

@@ -2310,11 +2310,10 @@ void wallet2::pull_and_parse_next_blocks(uint64_t start_height, uint64_t &blocks
     THROW_WALLET_EXCEPTION_IF(prev_blocks.size() != prev_parsed_blocks.size(), error::wallet_internal_error, "size mismatch");
 
     // prepend the last 3 blocks, should be enough to guard against a block or two's reorg
-    std::vector<parsed_block>::const_reverse_iterator i = prev_parsed_blocks.rbegin();
-    for (size_t n = 0; n < std::min((size_t)3, prev_parsed_blocks.size()); ++n)
+    auto s = std::next(prev_parsed_blocks.rbegin(), std::min((size_t)3, prev_parsed_blocks.size())).base();
+    for (; s != prev_parsed_blocks.end(); ++s)
     {
-      short_chain_history.push_front(i->hash);
-      ++i;
+      short_chain_history.push_front(s->hash);
     }
 
     // pull the new blocks