patch 8.2.1702: crash when using undo after deleting folded lines Commit: https://github.com/vim/vim/commit/da697645d5917eb3d4168c06c3442bef9fb746bf Author: Bram Moolenaar <Bram@vim.org> Date: Thu Sep 17 19:36:04 2020 +0200 patch 8.2.1702: crash when using undo after deleting folded lines Problem: Crash when using undo after deleting folded lines. Solution: Check for NULL pointer. (closes https://github.com/vim/vim/issues/6968)