For the purposes of Function.prototype.call, treated JS Null and Unde…

…fined objects as tho they were of type BoxedValue.

This fixes #38.

Signed-off-by: John Gietzen <otac0n@gietzen.us>

Src/IronJS/Native.Function.fs

@@ -129,7 +129,7 @@ module internal Function =
 
       let skip = if args.Length = 0 then 0 else 1
       let args = args |> Seq.skip skip |> Seq.toArray
-      let argsClr = args |> Array.map TC.ToClrObject
+      let argsClr = args |> Array.map (fun i -> if not i.IsNull && i.IsClr then TC.ToClrObject i else i :> obj)
       let argTypes = argsClr |> Array.map TypeUtils.getType
 
       let type' = argTypes $ DelegateUtils.getCallSiteDelegate