qt6: Handle QVariant changes in services API.

Need to create a null QVariant slightly differently in the Qt6
API. Create it once and use in multiple places, instead of creating it
anew each time.

mythtv/programs/mythbackend/services/myth.cpp

@@ -538,24 +538,25 @@ DTC::LogMessageList *Myth::GetLogs(  const QString   &HostName,
         }
         sql.append(" ORDER BY msgtime ASC;");
 
+#if QT_VERSION < QT_VERSION_CHECK(6,0,0)
+        QVariant ullNull = QVariant(QVariant::ULongLong);
+#else
+        QVariant ullNull = QVariant(QMetaType(QMetaType::ULongLong));
+#endif
         query.prepare(sql);
 
         query.bindValue(":HOSTNAME", (HostName.isEmpty()) ? QString() : HostName);
         query.bindValue(":APPLICATION", (Application.isEmpty()) ? QString() :
                                                                   Application);
-        query.bindValue(":PID", ( PID == 0 ) ? QVariant(QVariant::ULongLong) :
-                                               (qint64)PID);
-        query.bindValue(":TID", ( TID == 0 ) ? QVariant(QVariant::ULongLong) :
-                                               (qint64)TID);
+        query.bindValue(":PID", ( PID == 0 ) ? ullNull : (qint64)PID);
+        query.bindValue(":TID", ( TID == 0 ) ? ullNull : (qint64)TID);
         query.bindValue(":THREAD", (Thread.isEmpty()) ? QString() : Thread);
         query.bindValue(":FILENAME", (Filename.isEmpty()) ? QString() : Filename);
-        query.bindValue(":LINE", ( Line == 0 ) ? QVariant(QVariant::ULongLong) :
-                                                 (qint64)Line);
+        query.bindValue(":LINE", ( Line == 0 ) ? ullNull : (qint64)Line);
         query.bindValue(":FUNCTION", (Function.isEmpty()) ? QString() : Function);
         query.bindValue(":FROMTIME", (FromTime.isValid()) ? FromTime : QDateTime());
         query.bindValue(":TOTIME", (ToTime.isValid()) ? ToTime : QDateTime());
-        query.bindValue(":LEVEL", (Level.isEmpty()) ?
-                                        QVariant(QVariant::ULongLong) :
+        query.bindValue(":LEVEL", (Level.isEmpty()) ? ullNull :
                                         (qint64)logLevelGet(Level));
 
         if (!MsgContains.isEmpty())