src: ensure v8::Eternal is empty before setting it

V8 does not check this for us, but this is a requirement of the API.

PR-URL: #59825
Reviewed-By: James M Snell <[email protected]>
Reviewed-By: Chengzhong Wu <[email protected]>
Reviewed-By: Juan José Arboleda <[email protected]>

Author: addaleax

src/env-inl.h

@@ -839,6 +839,7 @@ void Environment::set_process_exit_handler(
     return PropertyName##_.Get(isolate_);                                      \
   }                                                                            \
   inline void IsolateData::set_##PropertyName(v8::Local<TypeName> value) {     \
+    CHECK(PropertyName##_.IsEmpty());                                          \
     PropertyName##_.Set(isolate_, value);                                      \
   }
   PER_ISOLATE_TEMPLATE_PROPERTIES(V)