Fix the width of the slider label when the number of layers was exactly

10, 100, 1000 and so on.

The calculation was using the maximumValue that is 9 in case we have 10
layers, since we start counting from 0 but showing from 1. Now it uses
maximumValue + 1.

plugins/SimulationView/SimulationSliderLabel.qml

@@ -48,7 +48,7 @@ UM.PointingRectangle {
             horizontalCenter: parent.horizontalCenter
         }
 
-        width: (maximumValue.toString().length + 1) * 10 * screenScaleFactor
+        width: ((maximumValue + 1).toString().length + 1) * 10 * screenScaleFactor
         text: sliderLabelRoot.value + startFrom // the current handle value, add 1 because layers is an array
         horizontalAlignment: TextInput.AlignRight