Rotating the device produces new history undo/redo entry

[mzorz]

I noticed that opening a post with any content, then rotating the device, will produce a new action in the undo/redo history. Tapping the back arrow won't update the Post given the content remains the same.

Steps to reproduce:

1. start a draft
2. enter a title and some content
3. tap BACK and wait for the draft to be uploaded
4. open the Post again without modifying it
5. rotate the device
6. observe the undo action is now available, for no apparent reason.

[guarani]

This issue will depend on #1751 being fixed first. At the moment, just opening the editor results in the undo button being enabled – so I think we'll have to fix that first before getting to this.