reimplement workaround for qdockwidget bug

mainwindow.cpp

@@ -62,8 +62,12 @@ void MainWindow::setup_layout() {
     addDockWidget(Qt::TopDockWidgetArea, panel_sequence_viewer);
 	addDockWidget(Qt::BottomDockWidgetArea, panel_timeline);
 
-	// workaround for older versions of Qt (but not too old)
-	layout()->update();
+    layout()->update();
+
+    // workaround for strange Qt dock bug (see https://bugreports.qt.io/browse/QTBUG-65592)
+#if QT_VERSION >= QT_VERSION_CHECK(5, 6, 0)
+    resizeDocks({panel_project}, {40}, Qt::Horizontal);
+#endif
 }
 
 MainWindow::MainWindow(QWidget *parent) :