Use DynamicResource for ValidationErrorTemplate inside TextBox (#2197)

Author: nejcgalof

MaterialDesignThemes.Wpf/Themes/MaterialDesignTheme.TextBox.xaml

@@ -27,7 +27,7 @@
         <Setter Property="Padding" Value="{x:Static wpf:Constants.TextBoxDefaultPadding}" />
         <Setter Property="ScrollViewer.PanningMode" Value="VerticalFirst"/>
         <Setter Property="Stylus.IsFlicksEnabled" Value="False"/>
-        <Setter Property="Validation.ErrorTemplate" Value="{StaticResource MaterialDesignValidationErrorTemplate}"/>
+        <Setter Property="Validation.ErrorTemplate" Value="{DynamicResource MaterialDesignValidationErrorTemplate}"/>
         <Setter Property="wpf:TextFieldAssist.UnderlineBrush" Value="{DynamicResource PrimaryHueMidBrush}" />
         <Setter Property="wpf:HintAssist.Foreground" Value="{DynamicResource PrimaryHueMidBrush}" />
         <Setter Property="ContextMenu" Value="{StaticResource MaterialDesignDefaultContextMenu}" />