[Merge chakra-core/ChakraCore@7f0403e0e8] [MERGE #3845 @obastemur] Ca…

…nonicalizeAccessor returns wrong results on cross thread

Merge pull request #3845 from obastemur:fix_ctt

`accessor` might be initialized under a different context hence `library->Undefined != accessor's->library->Undefined`

Recently added an Assert to IsUndefinedObject** checks. That assert helped revealing this issue.

See also https://github.com/Microsoft/ChakraCore/blame/master/lib/Runtime/Types/DictionaryTypeHandler.cpp#L2020

deps/chakrashim/core/lib/Runtime/Types/DictionaryTypeHandler.cpp

@@ -1986,7 +1986,7 @@ namespace Js
     template <typename T>
     Var DictionaryTypeHandlerBase<T>::CanonicalizeAccessor(Var accessor, /*const*/ JavascriptLibrary* library)
     {
-        if (accessor == nullptr || JavascriptOperators::IsUndefinedObject(accessor, library))
+        if (accessor == nullptr || JavascriptOperators::IsUndefinedObject(accessor))
         {
             accessor = library->GetDefaultAccessorFunction();
         }