Fix Travis build

src/MainWindow.cpp

@@ -27,6 +27,7 @@
 #include <QMessageBox>
 #include <QUrl>
 #include <QStandardItemModel>
+#include <QPersistentModelIndex>
 #include <QDragEnterEvent>
 #include <QScrollBar>
 #include <QSortFilterProxyModel>

src/MainWindow.h

@@ -12,6 +12,7 @@ class EditDialog;
 class QIntValidator;
 class QLabel;
 class QModelIndex;
+class QPersistentModelIndex;
 class SqliteTableModel;
 class DbStructureModel;
 class QNetworkReply;