src: add napi_define_class() null checks
napi_define_class is tested by passing NULL to all parameters that are pointers, one at a time. Moreover, two bugs were corrected. One was utf8name and the second was the property descriptor pointer. These pointers were assumed to be non-NULL and now we have NULL checks.
Checklist
-
make -j4 test
(UNIX), orvcbuild test
(Windows) passes -
tests and/or benchmarks are included -
commit message follows commit guidelines