Redraw text borders after toggling menu

Hi,

I have a similar question to #161

After toggling a [Table of Content,](https://github.com/plasticboy/vim-markdown#enable-toc-window-auto-fit) vim redraws the text area borders with a darker shade than the background, thus making them visibile.

See:

I'm using MacVim and [vim-color-pencil](https://github.com/reedes/vim-colors-pencil) as color-scheme.

Is the issue actually due to a failed redrawing of "text area" border? If so, how can I force a redrawing of those line?

Thank you in advance!

Reproduce the issue in MacVim with vim-colors-pencil: toggle the Table of Contents and compare the text-area borders before and after. Start by tracing the TOC toggle and Vim redraw behavior; done means the borders redraw with the intended contrast after toggling.

Written by the indexing model from the issue text.