Wrong Foreground style set for FlatButton

[Blinchik91]

Hi there,

I found a bug in "MaterialDesignTheme.Button.xaml" . There is a wrong foreground style set for MaterialDesignFlatButton.

    <Style x:Key="MaterialDesignFlatButton" TargetType="{x:Type ButtonBase}">
        <Setter Property="FocusVisualStyle" Value="{StaticResource FocusVisual}"/>
        <Setter Property="Background" Value="Transparent"/>
        <Setter Property="BorderBrush" Value="Transparent"/>
        <Setter Property="Cursor" Value="Hand"/>
        <Setter Property="Foreground" Value="{DynamicResource PrimaryHueMidBrush}"/>

The button text eg. in OpenDialog in Darkmode is not readable because it has nearly the same color as the background. It has to be "MaterialDesignBody" instead of "PrimaryHueMidBrush"

Because we want to switch the light modes

Can someone fix it ?