WP8, null value in LoopingSelector DataSource - windows-phone-8

Question

I am using Windows Phone Toolkit nuget package (http://phone.codeplex.com/). I want to create a LoopingSelector in my WP8 application, where I can select day dates, but I don't want the LoopingSelector to show days before today in it's selection.
My control looks like this:
http://s2.postimg.org/6bgnxefnt/image.png
This is perfectly working until I select the first element of the source (today Dec 04), then my application becomes unresponsive (I can press buttons, effect are shown, but the event handlers won't execute). I guess this is an infinite loop or deadlock, but it's not in my own code (I debugged it).
The definition of the LoopingSelector's data source:
public class NextDatesDataSource : LoopingDataSource<NextDateModel>
{
public NextDatesDataSource() : base(NextDateModel.Create(DateTime.Today)) { }
protected override NextDateModel GetNext(NextDateModel relativeTo)
{
if (relativeTo.Date == DateTime.Today + TimeSpan.FromDays(10))
return null;
return NextDateModel.Create(relativeTo.Date + TimeSpan.FromDays(1));
}
protected override NextDateModel GetPrevious(NextDateModel relativeTo)
{
//if i comment the next two lines, then everything works perfect
if (relativeTo.Date == DateTime.Today)
return null;
return NextDateModel.Create(relativeTo.Date - TimeSpan.FromDays(1));
}
}
LoopingDataSource:
public abstract class LoopingDataSource<T> : ILoopingSelectorDataSource
{
protected LoopingDataSource() { selectedItem = default(T); }
protected LoopingDataSource(T initialSelection) { selectedItem = initialSelection; }
protected abstract T GetNext(T relativeTo);
protected abstract T GetPrevious(T relativeTo);
public object GetNext(object relativeTo)
{
if (relativeTo == null) return null;
return GetNext((T)relativeTo);
}
public object GetPrevious(object relativeTo)
{
if (relativeTo == null) return null;
return GetPrevious((T)relativeTo);
}
private T selectedItem;
public object SelectedItem
{
get
{
return selectedItem;
}
set
{
object oldVal = selectedItem;
selectedItem = (T)value;
if (SelectionChanged != null)
SelectionChanged(this, new SelectionChangedEventArgs(new object[] { oldVal }, new object[] { value }));
}
}
public T Selected
{
get { return (T)SelectedItem; }
set { SelectedItem = value; }
}
public event EventHandler<SelectionChangedEventArgs> SelectionChanged;
}
The definition of the control element:
<p:LoopingSelector
x:Name="DaySelector"
Grid.Column="0" Grid.Row="1"
ItemSize="230,110"
ItemMargin="6" Margin="10,5,5,5">
<p:LoopingSelector.ItemTemplate>
<DataTemplate>
<Grid>
<TextBlock Text="{Binding Header}" FontSize="28" VerticalAlignment="Top"/>
<TextBlock Text="{Binding Body}" FontSize="42" FontWeight="Bold" VerticalAlignment="Bottom"/>
</Grid>
</DataTemplate>
</p:LoopingSelector.ItemTemplate>
</p:LoopingSelector>
I do this in the constructor:
DaySelector.DataSource = new NextDatesDataSource();
Thank you very much!