patch 8.2.1509: vertical separator is cleared when dragging a popup window Commit: https://github.com/vim/vim/commit/9943b3d97955ece99c747c959e0a7d493bb762bb Author: Bram Moolenaar <Bram@vim.org> Date: Sat Aug 22 17:21:14 2020 +0200 patch 8.2.1509: vertical separator is cleared when dragging a popup window Problem: Vertical separator is cleared when dragging a popup window using a multi-byte character for the border. Solution: Only clear the character before the window if it is using a multi-byte character. (closes #6766)