fix for #707
fix for #707

using the blog entry from Josh Smith
Binding to (Validation.Errors)[0] without Creating Debug Spew

http://joshsmithonwpf.wordpress.com/2008/10/08/binding-to-validationerrors0-without-creating-debug-spew/

batzen/MahApps.Metro,psinl/MahApps.Metro,Evangelink/MahApps.Metro,Danghor/MahApps.Metro,xxMUROxx/MahApps.Metro,pfattisc/MahApps.Metro,MahApps/MahApps.Metro,Jack109/MahApps.Metro,ye4241/MahApps.Metro,chuuddo/MahApps.Metro,p76984275/MahApps.Metro,jumulr/MahApps.Metro