Fixed error when saving unknown url in bookmark card (#11210)
Fixed error when saving unknown url in bookmark card (#11210)

no issue

- `payload.metadata` may not exist in a bookmark card because it's possible to save a mobiledoc document when the card is in it's "unable to parse url" state in the editor
- check for `payload.metadata` object before performing any url transformations to avoid invalid property access
JohnONolan/Ghost,e10/Ghost,bitjson/Ghost,kevinansfield/Ghost,kevinansfield/Ghost,Kikobeats/Ghost,TryGhost/Ghost,ErisDS/Ghost,bitjson/Ghost,Kikobeats/Ghost,Kikobeats/Ghost,ErisDS/Ghost,janvt/Ghost,kevinansfield/Ghost,ErisDS/Ghost,e10/Ghost,TryGhost/Ghost,JohnONolan/Ghost,TryGhost/Ghost,janvt/Ghost,JohnONolan/Ghost