Avoid Qt 6.8 bug

Still present in Qt 6.8.3, just calling setUrl
before adding the QWebEngineView to QDialog
avoids the issue and, since this is a reasonable
initialization anyway, it is done unconditionally.
https://bugreports.qt.io/browse/QTBUG-135002

src/Charts/PythonChart.cpp

@@ -438,6 +438,7 @@ PythonChart::setWeb(bool x)
 
         // setup the canvas
         canvas = new QWebEngineView(this);
+        canvas->setUrl(QUrl());
         canvas->setContentsMargins(0,0,0,0);
         canvas->setZoomFactor(dpiXFactor);
         canvas->setSizePolicy(QSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding));

src/Train/WebPageWindow.cpp

@@ -171,6 +171,8 @@ WebPageWindow::WebPageWindow(Context *context) : GcChartWindow(context), context
     connect(view->page()->profile(), SIGNAL(downloadRequested(QWebEngineDownloadRequest*)), this, SLOT(downloadRequested(QWebEngineDownloadRequest*)));
 #endif
     connect(view->page(), SIGNAL(linkHovered(QString)), this, SLOT(linkHovered(QString)));
+
+    forceReplot();
 }
 
 WebPageWindow::~WebPageWindow()