Fixed validation errors not showing after failed save in editor
Fixed validation errors not showing after failed save in editor

refs https://github.com/TryGhost/Admin/commit/99dc342a71cba7bae849780cc243c9c528b8c47d

- we weren't checking if an error was a validation error by examining the number of errors on the post model, this meant we weren't falling through to the generic error handling/display logic that shows an alert for validation errors when a save isn't a background/silent save

TryGhost/Ghost-Admin,TryGhost/Ghost-Admin