handsontable/handsontable — pull request #2012 by pcalchi (2014-12-30 18:00:45+00:00)
Title: Update json-patch-duplex.js

If oldVal is object and newVal is string or any primitive type a TypeError is thrown by the Object.keys function.

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/keys