fix build on Linux

ARRCON/ARRCON.cpp

@@ -345,7 +345,7 @@ int main_impl(const int argc, char** argv)
 			std::string str;
 			std::getline(std::cin, str);
 
-			// check for buffered data
+			// check for data remaining in the socket's buffer from previous commands
 			if (const auto& buffer_size{ client.buffer_size() }; buffer_size > 0) {
 				std::clog << MessageHeader(LogLevel::Warning) << "The buffer contains " << buffer_size << " unexpected bytes! Dumping the buffer to STDOUT." << std::endl;
 

ARRCON/net/rcon.hpp

@@ -308,7 +308,7 @@ namespace net {
 			buffer flush()
 			{
 				const auto bytes{ socket.available() };
-				if (bytes == 0) return;
+				if (bytes == 0) return {};
 
 				buffer p{ bytes, 0, std::allocator<uint8_t>() };
 				boost::asio::read(socket, boost::asio::buffer(p));