rest/rpc: Make mempoolinfo atomic

src/rpc/blockchain.cpp

@@ -1483,6 +1483,8 @@ static UniValue getchaintips(const JSONRPCRequest& request)
 
 UniValue MempoolInfoToJSON(const CTxMemPool& pool)
 {
+    // Make sure this call is atomic in the pool.
+    LOCK(pool.cs);
     UniValue ret(UniValue::VOBJ);
     ret.pushKV("size", (int64_t)pool.size());
     ret.pushKV("bytes", (int64_t)pool.GetTotalTxSize());