Fix frequent -netinfo JSON errors from null getpeerinfo#relaytxes

"error: JSON value is not a boolean as expected"

due to fRelayTxes/m_relay_txs being moved in PR 21160 from CNodeStats to
CNodeStateStats, which made getpeerinfo#relaytxes an optional field that
can return UniValue IsNull().

Author: jonatack

src/bitcoin-cli.cpp

@@ -477,7 +477,7 @@ class NetinfoRequestHandler : public BaseRequestHandler
             const int8_t network_id{NetworkStringToId(network)};
             if (network_id == UNKNOWN_NETWORK) continue;
             const bool is_outbound{!peer["inbound"].get_bool()};
-            const bool is_block_relay{!peer["relaytxes"].get_bool()};
+            const bool is_block_relay{peer["relaytxes"].isNull() ? false : !peer["relaytxes"].get_bool()};
             const std::string conn_type{peer["connection_type"].get_str()};
             ++m_counts.at(is_outbound).at(network_id);      // in/out by network
             ++m_counts.at(is_outbound).at(NETWORKS.size()); // in/out overall