 [Wpf] Fix bug inserting row before intended row in ListDataSource (#764)
 [Wpf] Fix bug inserting row before intended row in ListDataSource (#764)

also causing exception for row zero.

hamekoz/xwt,lytico/xwt,mono/xwt,antmicro/xwt,hwthomas/xwt,TheBrainTech/xwt