Add some missing type checks in dynamic.c++.
Add some missing type checks in dynamic.c++.

bsn069/capnproto,a-richardson/capnproto,johnkdoe/capnproto,mologie/capnproto,jparyani/capnproto,bryce-gibson/capnproto,zarvox/capnproto,kamalmarhubi/capnproto,martindale/capnproto,hntrmrrs/capnproto,kamalmarhubi/capnproto,modulexcite/capnproto,khklau/capnproto,Fraser999/capnproto,Fraser999/capnproto,ocdtrekkie/capnproto,vladon/capnproto,ocdtrekkie/capnproto,maurer/capnproto,johnkdoe/capnproto,artillery/capnproto,mologie/capnproto,khklau/capnproto,a-richardson/capnproto,hntrmrrs/capnproto,joliss/capnproto,artillery/capnproto,geofft/capnproto,modulexcite/capnproto,a-richardson/capnproto,ligzy/capnproto,MarPiRK/capnproto,jparyani/capnproto,pjulien/capnproto,Fraser999/capnproto,vladon/capnproto,ligzy/capnproto,geofft/capnproto,mrdomino/capnproto,nagyistoce/capnproto,martindale/capnproto,rcrowder/capnproto,mrdomino/capnproto,khklau/capnproto,maurer/capnproto,hntrmrrs/capnproto,pjulien/capnproto,johnkdoe/capnproto,bsn069/capnproto,bryce-gibson/capnproto,mologie/capnproto,martindale/capnproto,MarPiRK/capnproto,nagyistoce/capnproto,pjulien/capnproto,artillery/capnproto,nagyistoce/capnproto,MarPiRK/capnproto,rcrowder/capnproto,zarvox/capnproto,maurer/capnproto,bsn069/capnproto,ligzy/capnproto,bryce-gibson/capnproto,rcrowder/capnproto,ocdtrekkie/capnproto,vladon/capnproto,zarvox/capnproto,jparyani/capnproto,modulexcite/capnproto,mrdomino/capnproto,joliss/capnproto,joliss/capnproto,kamalmarhubi/capnproto,geofft/capnproto