Fix intermittent incorrectly set error object on successful dbus call

tqdbusconnection.cpp

@@ -29,6 +29,8 @@
 #include "tqdbusmessage.h"
 #include "tqdbusconnection_p.h"
 
+#include "tqdbusmessage_p.h"
+
 QT_STATIC_CONST_IMPL char *TQT_DBusConnection::default_connection_name = "qt_dbus_default_connection";
 
 class TQT_DBusConnectionManager
@@ -280,12 +282,23 @@ TQT_DBusMessage TQT_DBusConnection::sendWithReply(const TQT_DBusMessage &message
         return TQT_DBusMessage::fromDBusMessage(0);
     DBusMessage *reply = dbus_connection_send_with_reply_and_block(d->connection, msg,
                                                 -1, &d->error);
+
     if (d->handleError() && error)
         *error = d->lastError;
 
     dbus_message_unref(msg);
 
-    return TQT_DBusMessage::fromDBusMessage(reply);
+    TQT_DBusMessage ret = TQT_DBusMessage::fromDBusMessage(reply);
+
+    // HACK
+    // Reset the error object if no error was reported by DBus
+    // This is needed because TQT_DBusMessage::fromDBusMessage sometimes sets the error object even if DBus did not report a fatal error,
+    // and the dbus_error_is_set() check cannot be moved inside fromDBusMessage() without breaking the API and ABI.
+    if (!dbus_error_is_set(&d->error)) {
+        ret.d->error = TQT_DBusError();
+    }
+
+    return ret;
 }
 
 void TQT_DBusConnection::flush() const