Fix 'kube apply' panic on nil items

Bug 1146024 - https://bugzilla.redhat.com/show_bug.cgi?id=1146024
@smarterclayton I didn't figure out why the
`fakeScheme.AddKnownTypeWithName("v1beta1", "FakeResource", &FakeResource{})`
returned `Failed to create Config.items[0] of 'kind=FakeResource': No version ''` error triggered by `conversion.NewObject()` <- `Decode()` <- `client.Do().Get()`)