Undo not working anymore - a.done is undefined resp. hist.done is undefined

[q2apro]

Hi, I love using codemirror in the latest modx evolution (1.0.14). Problem is that (I guess after some modifications that I unforatunately cannot recall) the live-saving undo-feature using CTRL+Z does not work anymore. I cannot figure out the exact reason but I could track down the error to line:

hist.done = copyHistoryArray(histData.done.slice(0), null, true);

Found in setHistory: function(histData) {

Using console.log I see that histData and the hist object have: History { length: 3, state: null }. But there is no histData.done.

Can someone help?