Calling routine for instantiating built-ins' properties only if property name is a magic string.

src/libecmabuiltins/ecma-builtin-internal-routines-template.inc.h

@@ -109,10 +109,8 @@ TRY_TO_INSTANTIATE_PROPERTY_ROUTINE_NAME (BUILTIN_UNDERSCORED_ID) (ecma_object_t
 
   ecma_magic_string_id_t id;
 
-  if (!ecma_is_string_magic (prop_name_p, &id))
-  {
-    return NULL;
-  }
+  bool is_string_magic = ecma_is_string_magic (prop_name_p, &id);
+  JERRY_ASSERT (is_string_magic);
 
   int32_t index;
   index = ecma_builtin_bin_search_for_magic_string_id_in_array (ecma_builtin_property_names,