Crucial bug fix to outline shader

Fixed a bug that made the outline color inside the outline. It now only colors the outline. This happened in conjunction with using a specific drawing tool. But it's now fixed. I know the outline shader seems really popular amongst youtubers, sticker makers, and possibly more. I'm happy to have it fixed, sorry that it took awhile. I knew about this when I streamed on twitch a few days ago but I was painting until I found more bugs.