minor modified style

src/Shared/HandyControl_Shared/Themes/Styles/Button.xaml

@@ -46,6 +46,7 @@
     <Style x:Key="ButtonIcon" BasedOn="{StaticResource ButtonBaseStyle}" TargetType="Button">
         <Setter Property="Background" Value="Transparent"/>
         <Setter Property="BorderBrush" Value="Transparent"/>
+        <Setter Property="Foreground" Value="{DynamicResource PrimaryTextBrush}"/>
         <Setter Property="hc:BorderElement.CornerRadius" Value="0"/>
         <Setter Property="Template">
             <Setter.Value>