Merge with master
Fix memberwise clone of null Nullable (#477)

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extra : source : a4959c47ff3dd0ff6def8964c39fdf2ad5147fe1
extra : amend_source : eb9f13f568af7c6999b23624e5e387958ca87374
Test case for Nullable modification added.

--HG--
extra : amend_source : fb753e349de09beac692a3bba2d5308a86a8a68a
Merge with updated Nullable

--HG--
extra : amend_source : 3656a6752b5141d3b9a08b18f6212d63b9688b04