Fix #5553

Make sure the tip hash still matches the cached block

src/cryptonote_core/blockchain.cpp

@@ -1369,7 +1369,8 @@ bool Blockchain::create_block_template(block& b, const crypto::hash *from_block,
     // just as we compare it, we'll just use a slightly old template, but
     // this would be the case anyway if we'd lock, and the change happened
     // just after the block template was created
-    if (!memcmp(&miner_address, &m_btc_address, sizeof(cryptonote::account_public_address)) && m_btc_nonce == ex_nonce && m_btc_pool_cookie == m_tx_pool.cookie()) {
+    if (!memcmp(&miner_address, &m_btc_address, sizeof(cryptonote::account_public_address)) && m_btc_nonce == ex_nonce
+      && m_btc_pool_cookie == m_tx_pool.cookie() && m_btc.prev_id == get_tail_id()) {
       MDEBUG("Using cached template");
       m_btc.timestamp = time(NULL); // update timestamp unconditionally
       b = m_btc;