Fix possible terminate called for uncaught exception in Connection

src/Client/Connection.cpp

@@ -232,12 +232,27 @@ void Connection::disconnect()
     maybe_compressed_out = nullptr;
     in = nullptr;
     last_input_packet_type.reset();
-    out = nullptr; // can write to socket
+    std::exception_ptr finalize_exception;
+    try
+    {
+        // finalize() can write to socket and throw an exception.
+        out->finalize();
+    }
+    catch (...)
+    {
+        /// Don't throw an exception here, it will leave Connection in invalid state.
+        finalize_exception = std::current_exception();
+    }
+    out = nullptr;
+
     if (socket)
         socket->close();
     socket = nullptr;
     connected = false;
     nonce.reset();
+
+    if (finalize_exception)
+        std::rethrow_exception(finalize_exception);
 }