fix crash on unknown timezone in tz helper

src/node_cctz.cc

@@ -31,7 +31,12 @@ NAN_METHOD(load_time_zone) {
 		return;
 	}
 
-	std::unique_ptr<Nan::Persistent<v8::Object>> persist(new Nan::Persistent<v8::Object>(TimeZone::NewInstance(info[0])));
+	auto tz = TimeZone::NewInstance(info[0]);
+	if (tz.IsEmpty()) {
+		return;
+	}
+
+	std::unique_ptr<Nan::Persistent<v8::Object>> persist(new Nan::Persistent<v8::Object>(tz.ToLocalChecked()));
 	info.GetReturnValue().Set(Nan::New(*persist));
 	time_zone_map[name] = std::move(persist);
 }

src/timezone.cc

@@ -105,15 +105,15 @@ NAN_METHOD(TimeZone::New) {
 	info.GetReturnValue().Set(info.This());
 }
 
-v8::Local<v8::Object> TimeZone::NewInstance() {
+v8::MaybeLocal<v8::Object> TimeZone::NewInstance() {
 	v8::Local<v8::Function> cons = Nan::New(constructor);
-	return Nan::NewInstance(cons).ToLocalChecked();
+	return Nan::NewInstance(cons);
 }
 
-v8::Local<v8::Object> TimeZone::NewInstance(v8::Local<v8::Value> arg) {
+v8::MaybeLocal<v8::Object> TimeZone::NewInstance(v8::Local<v8::Value> arg) {
 	const unsigned argc = 1;
 	v8::Local<v8::Value> argv[argc] = { arg };
 	v8::Local<v8::Function> cons = Nan::New<v8::Function>(constructor);
 
-	return Nan::NewInstance(cons, argc, argv).ToLocalChecked();
+	return Nan::NewInstance(cons, argc, argv);
 }

src/timezone.h

@@ -8,8 +8,8 @@
 class TimeZone : public Nan::ObjectWrap {
 public:
 	static NAN_MODULE_INIT(Init);
-	static v8::Local<v8::Object> NewInstance();
-	static v8::Local<v8::Object> NewInstance(v8::Local<v8::Value> arg);
+	static v8::MaybeLocal<v8::Object> NewInstance();
+	static v8::MaybeLocal<v8::Object> NewInstance(v8::Local<v8::Value> arg);
 	static Nan::Persistent<v8::FunctionTemplate> prototype;
 
 	cctz::time_zone value;

test.js

@@ -180,6 +180,11 @@ test('TimeZone has name getter', t => {
 	t.is(new TimeZone('UTC').name, 'UTC');
 });
 
+test('tz shortcut workd', t => {
+	t.throws(() => tz('unknown'), 'Failed to load time zone unknown');
+	t.is(tz('UTC').name, 'UTC');
+});
+
 test('now shortcut works', t => {
 	t.is(now(), Math.floor(Date.now() / 1000));
 });