Koenig - Fix PSM meta/twitter/facebook pane errors on new posts
Koenig - Fix PSM meta/twitter/facebook pane errors on new posts

refs https://github.com/TryGhost/Ghost/issues/9623
- do not assume that a markdown card exists when generating the SEO description preview

kevinansfield/Ghost-Admin,TryGhost/Ghost-Admin,TryGhost/Ghost-Admin,kevinansfield/Ghost-Admin