Update the transfer function before updating the current point

If the current point is the last point, and a point is added anywhere
before the last point, there was an assert, because the new number of points
wasn't updated (max of the spinbox), however the current point id was
incremented.

Libs/Visualization/VTK/Widgets/ctkVTKScalarsToColorsWidget.cpp

@@ -265,13 +265,24 @@ void ctkVTKScalarsToColorsWidget::onBoundsChanged()
 // ----------------------------------------------------------------------------
 void ctkVTKScalarsToColorsWidget::setCurrentPoint(vtkObject* caller, void* callData)
 {
+  Q_D(ctkVTKScalarsToColorsWidget);
   vtkControlPointsItem* controlPoints = reinterpret_cast<vtkControlPointsItem*>(caller);
   long newPoint = reinterpret_cast<long>(callData);
   if (!controlPoints || newPoint < -1)
     {
     return;
     }
-  this->setCurrentControlPointsItem(controlPoints);
+  if (d->CurrentControlPointsItem != item)
+    {
+    this->setCurrentControlPointsItem(controlPoints);
+    }
+  else
+    {
+    // When a new point is added, the modified event is fired later.
+    // however we need to update the max of the current spin box before
+    // setting the new value.
+    this->updateCurrentPoint();
+    }
   this->setCurrentPoint(newPoint);
 }