blockchain: add scope guard to waiter for threaded txv1 verification

src/cryptonote_core/blockchain.cpp

@@ -2658,6 +2658,7 @@ bool Blockchain::check_tx_inputs(transaction& tx, tx_verification_context &tvc,
 
   tools::threadpool& tpool = tools::threadpool::getInstance();
   tools::threadpool::waiter waiter;
+  const auto waiter_guard = epee::misc_utils::create_scope_leave_handler([&]() { waiter.wait(); });
   int threads = tpool.get_max_concurrency();
 
   for (const auto& txin : tx.vin)