Add fallback value to binding to avoid division by NaN

The bound value can become NaN when the control is Unloaded. To avoid exceptions, I simply apply a fallback value of 0.

Author: nicolaihenriksen

src/MaterialDesignThemes.Wpf/Themes/MaterialDesign3.ToggleButton.xaml

@@ -377,15 +377,15 @@
                 </DoubleAnimation>
                 <DoubleAnimation Storyboard.TargetName="Thumb"
                                  Storyboard.TargetProperty="Width"
-                                 To="{Binding Tag, ElementName=SwitchGrid}"
+                                 To="{Binding Tag, ElementName=SwitchGrid, FallbackValue=0}"
                                  Duration="0:0:0.2">
                   <DoubleAnimation.EasingFunction>
                     <QuadraticEase EasingMode="EaseOut" />
                   </DoubleAnimation.EasingFunction>
                 </DoubleAnimation>
                 <DoubleAnimation Storyboard.TargetName="Thumb"
                                  Storyboard.TargetProperty="Height"
-                                 To="{Binding Tag, ElementName=SwitchGrid}"
+                                 To="{Binding Tag, ElementName=SwitchGrid, FallbackValue=0}"
                                  Duration="0:0:0.16">
                   <DoubleAnimation.EasingFunction>
                     <QuadraticEase EasingMode="EaseOut" />
@@ -399,11 +399,11 @@
                                  Duration="0" />
                 <DoubleAnimation Storyboard.TargetName="Thumb"
                                  Storyboard.TargetProperty="Width"
-                                 To="{Binding Tag, ElementName=SwitchGrid}"
+                                 To="{Binding Tag, ElementName=SwitchGrid, FallbackValue=0}"
                                  Duration="0" />
                 <DoubleAnimation Storyboard.TargetName="Thumb"
                                  Storyboard.TargetProperty="Height"
-                                 To="{Binding Tag, ElementName=SwitchGrid}"
+                                 To="{Binding Tag, ElementName=SwitchGrid, FallbackValue=0}"
                                  Duration="0" />
               </Storyboard>
             </Grid.Resources>