GraphPanel widget: improved our removeAllGraphPanels() method (openco…

…r#1426).

Indeed, until now, we were removing all the graph panels, but the first
one. This was not only arbitrary, but if the graph panel had been
customised (e.g., a title had been set), then it means that it would
still be there. So, now, we add a graph panel (since we need at least
one graph panel) and then really remove all the other graph panels.

src/plugins/simulation/SimulationExperimentView/src/simulationexperimentviewsimulationwidget.cpp

@@ -2435,8 +2435,7 @@ bool SimulationExperimentViewSimulationWidget::furtherInitialize()
 
     GraphPanelWidget::GraphPanelsWidget *graphPanelsWidget = mContentsWidget->graphPanelsWidget();
 
-    while (graphPanelsWidget->graphPanels().count() != 1)
-        graphPanelsWidget->removeCurrentGraphPanel();
+    graphPanelsWidget->removeAllGraphPanels();
 
     // Add some graph panels, so that their number corresponds to the number of
     // 2D outputs mentioned in the SED-ML file, and select the first one

src/plugins/widget/GraphPanelWidget/src/graphpanelswidget.cpp

@@ -291,17 +291,13 @@ bool GraphPanelsWidget::removeCurrentGraphPanel()
 
 void GraphPanelsWidget::removeAllGraphPanels()
 {
-    // Make sure that we don't have only one graph panel left
-
-    if (mGraphPanels.count() == 1)
-        return;
+    // Remove all the graph panels, after having created an 'empty' one (since
+    // we want at least one graph panel at any given point in time)
 
-    // Remove all the graph panels but one
-    // Note: the one we keep is the very first one since it may be the user's
-    //       most important graph panel...
+    addGraphPanel();
 
     while (mGraphPanels.count() > 1)
-        removeGraphPanel(mGraphPanels.last());
+        removeGraphPanel(mGraphPanels.first());
 }
 
 //==============================================================================