Drafts are not deleted if they're edited right before deletion

[vickychijwani]

• Ghost version: 0.11.3
• App version: 1.5.1

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Steps to reproduce:

1. Create a new draft / open an existing draft
2. Type something
3. Try to delete it

The app comes back to the post list and says "Post deleted", but nothing actually happens. However if the draft is opened and deleted without making any edits first, it works.