patch 8.2.1731: Vim9: cannot use += to append to empty NULL list Commit: https://github.com/vim/vim/commit/81ed4960482f8baabdd7f95b4d5e39744be88ae7 Author: Bram Moolenaar <Bram@vim.org> Date: Wed Sep 23 15:56:50 2020 +0200 patch 8.2.1731: Vim9: cannot use += to append to empty NULL list Problem: Vim9: cannot use += to append to empty NULL list. Solution: Copy the list instead of extending it. (closes https://github.com/vim/vim/issues/6998)