Use optional chaining

Author: billouboq

src/parser/deserializer.ts

@@ -241,7 +241,7 @@ function deserializeObject(
 
     // shouldValidateKey is true if the key should be validated, false otherwise
     let shouldValidateKey = true;
-    if (globalUTFValidation || (utf8KeysSet && utf8KeysSet.has(name))) {
+    if (globalUTFValidation || utf8KeysSet?.has(name)) {
       shouldValidateKey = validationSetting;
     } else {
       shouldValidateKey = !validationSetting;