Regression: Document is marked dirty (discard popup on close) on edit even when nothing is changed

When document is opened in edit mode it is always marked as dirty and save/discard dialog is shown, even when no changes are done

Steps to reproduce
1) In GoGreen , Create a new document. In Go Green go to Hippo Duurzaam/Evenementen/2010 and create new event
2) Fill in a valid name, give the document a valid title
3) Save & Close
4) Click Edit. Do not edit anything
5) Click Save
6) Click the close-cross button on the tab to close the document
Expected: Document is closed
Actual: Dialog is displayed to stating the document has been modified