Fix reflect panic in runtime/conversion

Fixes `panic: reflect: call of reflect.Value.Type on zero Value`
when calling conversion.EnforcePtr() or
runtime.Scheme.ObjectVersionAndKind() from default type switch.

Signed-off-by: Vojtech Vitek (V-Teq) <vvitek@redhat.com>
Handle nil values in conversion.EnforcePtr()

Signed-off-by: Vojtech Vitek (V-Teq) <vvitek@redhat.com>
Use conversion.EnforcePtr() where appropriate

Signed-off-by: Vojtech Vitek (V-Teq) <vvitek@redhat.com>
Merge pull request #2001 from VojtechVitek/fix_scheme_panic

Fix reflect panic in runtime/conversion