TypeError when deleting an element

[flack]

To reproduce:

• Add a new child element somewhere
• Click save
• select the child element
• Click delete

result:

TypeError: model.change is not a function
create.js
Line 2420

[flack]

P.S.: the error message is from Firefox, in Chrome the wording is different, but refers to the same line:

Uncaught TypeError: undefined is not a function 
create.js:2420