Session.GetObject in Tridion 2011 returns component for non-existing item
===

I'm trying to figure out how to check if a component is null (e.g. not found in Tridion) in a custom backend. I just don't see how to check this, other than catching the error.

    Component comp = (Component)session.GetObject(base.ComponentUri);

    if (component != null)
    {
        bool isCheckedOut = component.IsCheckedOut;
    }
    else
    {
        // how do I get in here!
    }

I'm 100% sure the uri is correct ('tcm:113-438134') and 100% sure that there's no item in Tridion with that URI. 
The code above will throw an error at component.IsCheckedOut:

    The item tcm:113-438134-16 does not exist.

How do I check the existence of a Tridion item? 
I've tried placing the cast at the end, which didn't help much:

    Component comp = session.GetObject(base.ComponentUri) as Component;

and I've tried not casting at all but using an IdentifiableObject, which also didn't make any difference.
Anyone knows how to do this?