RFR (XS) 8247220: Make OopHandle constructor explicit

[Lois Foltan]

Looks good Coleen.
Lois

On 6/9/2020 10:36 AM, coleen.phillimore at oracle.com wrote:
> Summary: Fix null initializations to explicitly call the OopHandle 
> constructor
>
> See bug report for details.  Tested with tier1-3
>
> open webrev at http://cr.openjdk.java.net/~coleenp/2020/8247220.01/webrev
> bug link https://bugs.openjdk.java.net/browse/JDK-8247220
>
> Thanks,
> Coleen