Fixed compilation failure in Qt6

Added Compatibility for Qt6 of QVariant's deprecated members

src/contentmanagermodel.cpp

@@ -36,8 +36,13 @@ QVariant ContentManagerModel::data(const QModelIndex& index, int role) const
 
         r = getThumbnail(r);
 
+#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
         if ( r.type() == QVariant::ByteArray )
             return r;
+#else
+        if ( r.typeId() == QMetaType::QByteArray )
+            return r;
+#endif
 
         const QString faviconUrl = r.toString();
         if ( !faviconUrl.isEmpty() )
@@ -136,8 +141,13 @@ void ContentManagerModel::setBooksData(const BookInfoList& data, const Downloads
 // QString) from where the actual data can be obtained.
 QVariant ContentManagerModel::getThumbnail(const QVariant& faviconEntry) const
 {
+#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
     if ( faviconEntry.type() == QVariant::ByteArray )
         return faviconEntry;
+#else
+    if ( faviconEntry.typeId() == QMetaType::QByteArray )
+        return faviconEntry;
+#endif
 
     const auto faviconUrl = faviconEntry.toString();
     return m_iconMap.contains(faviconUrl)