Commented Unassigned: Zoombox Stack Overflow [20652]

Hi,

When using a simple ZoomBox like this :
```
<StackPanel>
<Grid Width="300"
Height="500">
<xctk:Zoombox x:Name="zoombox">
<Image Source="Resources/Default.jpg"/>
</xctk:Zoombox>
</Grid>
<Button Content="My Button"
Click="Button_Click_1" />
</StackPanel>
```

The ZoomBox.DataContext is null by default. If I try to change it in the Button_Click_1 callback, no exceptions are raised in v2.0.