Fix result of Date getters when called on invalid date (#3879)

Fixes #3878.

JerryScript-DCO-1.0-Signed-off-by: Dániel Bátyai dbatyai@inf.u-szeged.hu

jerry-core/ecma/builtin-objects/ecma-builtin-date-prototype.c

@@ -237,7 +237,7 @@ ecma_builtin_date_prototype_dispatch_get (uint16_t builtin_routine_id, /**< buil
 {
   if (ecma_number_is_nan (date_num))
   {
-    return ecma_make_magic_string_value (LIT_MAGIC_STRING_NAN);
+    return ecma_make_nan_value ();
   }
 
   switch (builtin_routine_id)

tests/jerry/regression-test-issue-3878.js

@@ -0,0 +1,21 @@
+// Copyright JS Foundation and other contributors, http://js.foundation
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+var d = new Date();
+
+var s = d.setHours();
+assert (typeof s === "number" && isNaN (s));
+
+var g = d.getHours();
+assert (typeof g === "number" && isNaN (g));