Use only single database

database.h

@@ -10,6 +10,7 @@
 class Database : public QObject
 {
     Q_OBJECT
+    QSqlDatabase database;
     QSqlQuery m_markQuery;
     QSqlQuery m_unmarkQuery;
     QSqlQuery m_isMarkedQuery;
@@ -40,7 +41,7 @@ protected:
     bool indexDir2(const QDir &dir, QProgressDialog *progress, QStringList &scannedDirs);
     bool indexFile(const QFileInfo &file);
     bool checkError(QSqlQuery &query);
-    int checkVersion();
+    int checkVersion(QSqlDatabase &db);
 signals:
     void databaseChanged();
 };