Backport ClickHouse#89740 to 25.8: Avoid crash due to reading from remote server after disconnect in remote queries during cancellation

Author: robot-clickhouse

src/Client/Connection.cpp

@@ -1000,7 +1000,7 @@ void Connection::sendCancel()
 {
     /// If we already disconnected.
     if (!out)
-        return;
+        throw Exception(ErrorCodes::NETWORK_ERROR, "Connection to {} terminated", getDescription());
 
     writeVarUInt(Protocol::Client::Cancel, *out);
     out->finishChunk();