Add a test for adopting a null pointer just to be safe.
Add a test for adopting a null pointer just to be safe.

mrdomino/capnproto,maurer/capnproto,hntrmrrs/capnproto,maurer/capnproto,hntrmrrs/capnproto,hntrmrrs/capnproto,pjulien/capnproto,mologie/capnproto,maurer/capnproto,pjulien/capnproto,mrdomino/capnproto,jparyani/capnproto,mologie/capnproto,jparyani/capnproto,jparyani/capnproto,mologie/capnproto,mrdomino/capnproto,pjulien/capnproto