ListBox DataTemplate - Displaying Image/Not displaying Image

Hi,

I am using a list box with the following data template and I am filling the item list from my messageitem class which contains the message and the path to an image. 

The problem I have is that the image is a correct mark which is displayed when a task completes. Prior to the task completing I am updating a single object in the listbox to displaying waiting.... ( like this )

waiting.

waiting..

waiting...

waiting... etc

Because at this point, I am passing in a bogus path to an image, my app throws out an exception each time on the output console due to the fact it can not find the image. Is there any way, i can have the image as an optional member or do something a little tidier? 

thanks,

ro

<ListBox IsHitTestVisible="False" ScrollViewer.VerticalScrollBarVisibility="Auto" ScrollViewer.CanContentScroll="True" BorderThickness="0" Background="Transparent" Name="lstCheckCardMessages" FlowDirection="LeftToRight" SelectionMode="Single"><ListBox.ItemTemplate><DataTemplate><StackPanel><StackPanel Orientation="Horizontal"><TextBlock Text="{Binding Path=Message}" Width="250" Padding="5" FontSize="16" Foreground="Black"></TextBlock><Image Source="{Binding Path=Imagesource}" Height="50"/></StackPanel></StackPanel></DataTemplate></ListBox.ItemTemplate></ListBox>