Fix prompt if default not found
Fix prompt if default not found

("string") was a malformed function call!

fsharp/fsharpbinding,nosami/xamarin-monodevelop-fsharp-addin,Ming-Tang/fsharpbinding,nosami/xamarin-monodevelop-fsharp-addin,fsharp/xamarin-monodevelop-fsharp-addin,fsharp/fsharpbinding,fsharp/xamarin-monodevelop-fsharp-addin,fsharp/fsharpbinding,Ming-Tang/fsharpbinding,Ming-Tang/fsharpbinding