fs: fix return value of fs APIs

Author: theanarkh

src/node_file-inl.h

@@ -287,20 +287,24 @@ FSReqBase* GetReqWrap(const v8::FunctionCallbackInfo<v8::Value>& args,
                       int index,
                       bool use_bigint) {
   v8::Local<v8::Value> value = args[index];
+  FSReqBase* result = nullptr;
   if (value->IsObject()) {
-    return BaseObject::Unwrap<FSReqBase>(value.As<v8::Object>());
-  }
-
-  Realm* realm = Realm::GetCurrent(args);
-  BindingData* binding_data = realm->GetBindingData<BindingData>();
-
-  if (value->StrictEquals(realm->isolate_data()->fs_use_promises_symbol())) {
-    if (use_bigint) {
-      return FSReqPromise<AliasedBigInt64Array>::New(binding_data, use_bigint);
-    } else {
-      return FSReqPromise<AliasedFloat64Array>::New(binding_data, use_bigint);
+    result = BaseObject::Unwrap<FSReqBase>(value.As<v8::Object>());
+  } else {
+    Realm* realm = Realm::GetCurrent(args);
+    BindingData* binding_data = realm->GetBindingData<BindingData>();
+
+    if (value->StrictEquals(realm->isolate_data()->fs_use_promises_symbol())) {
+      if (use_bigint) {
+        result = FSReqPromise<AliasedBigInt64Array>::New(binding_data, use_bigint);
+      } else {
+        result = FSReqPromise<AliasedFloat64Array>::New(binding_data, use_bigint);
+      }
     }
   }
+  if result != nullptr {
+    result->SetReturnValue(args);
+  }
   return nullptr;
 }
 
@@ -320,10 +324,7 @@ FSReqBase* AsyncDestCall(Environment* env, FSReqBase* req_wrap,
     uv_req->path = nullptr;
     after(uv_req);  // after may delete req_wrap if there is an error
     req_wrap = nullptr;
-  } else {
-    req_wrap->SetReturnValue(args);
   }
-
   return req_wrap;
 }