Fix the Object.getPrototypeOf function.

jerry-core/ecma/builtin-objects/ecma-builtin-object.cpp

@@ -128,11 +128,17 @@ ecma_builtin_object_object_get_prototype_of (ecma_value_t this_arg __attr_unused
   {
     /* 2. */
     ecma_object_t *obj_p = ecma_get_object_from_value (arg);
-
     ecma_object_t *prototype_p = ecma_get_object_prototype (obj_p);
-    ecma_ref_object (prototype_p);
 
-    ret_value = ecma_make_normal_completion_value (ecma_make_object_value (prototype_p));
+    if (prototype_p)
+    {
+      ret_value = ecma_make_normal_completion_value (ecma_make_object_value (prototype_p));
+      ecma_ref_object (prototype_p);
+    }
+    else
+    {
+      ret_value = ecma_make_simple_completion_value (ECMA_SIMPLE_VALUE_NULL);
+    }
   }
 
   return ret_value;

tests/jerry/object-create.js

@@ -128,8 +128,7 @@ try {
 // Create an object with null as prototype
 var obj = Object.create(null)
 assert (typeof (obj) === "object");
-// FIXME: enable this assertion after the #208 is fixed.
-// assert (Object.getPrototypeOf (obj) === null);
+assert (Object.getPrototypeOf (obj) === null);
 
 try {
     Object.create()

tests/jerry/object-getprototypeof.js

@@ -35,11 +35,21 @@ try {
   assert (e instanceof TypeError);
 }
 
+try {
+  var y = Object.getPrototypeOf(null);
+  assert (false);
+} catch (e) {
+  assert (e instanceof TypeError);
+}
+
 var obj = { x : "foo" };
-assert (Object.getPrototypeOf(obj) === Object.prototype)
+assert (Object.getPrototypeOf(obj) === Object.prototype);
 
 var constructor = function () {};
 constructor.prototype = obj;
 
 var d_obj = new constructor();
 assert (Object.getPrototypeOf(d_obj) === obj);
+
+obj = Object.create(null);
+assert (Object.getPrototypeOf(obj) === null);