Created Issue: RichTextBoxFormatBar: WPF Bug with SystemFontFamilies [19552]

From this [discussion](http://wpftoolkit.codeplex.com/discussions/438775)
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Hi,

could you please change the following:

combox.ItemsSource = Fonts.SystemFontFamilies ....

to:

http://code.logos.com/blog/2012/11/how-to-crash-many-wpf-applications-wpf-4-edition.html

Thanks!