patch 8.2.0633: crash when using null partial in filter() Commit: https://github.com/vim/vim/commit/9d8d0b5c644ea53364d04403740b3f23e57c1497 Author: Bram Moolenaar <Bram@vim.org> Date: Fri Apr 24 22:47:31 2020 +0200 patch 8.2.0633: crash when using null partial in filter() Problem: Crash when using null partial in filter(). Solution: Fix crash. Add more tests. (Yegappan Lakshmanan, closes https://github.com/vim/vim/issues/5976)