[BUG] (Un)selecting a class in the StyleManager throws a TypeError

Hello,

I am running into an issue when selecting or unselecting a class on an element in the StyleManager through the UI. This happens on both my own project and the newletter demo from the GrapesJS page.

It happens on version 0.14.61 which should be the current version.

Reproduction:

1. Open the newletter demo from the GrapesJS homepage.
2. Click on the big GrapesJS image and go to the StyleManager.
3. (Un)select the checkbox next to the class.
4. Observe an uncaught TypeError in your console.

I have included screenshots that ought to suffice, please let me know if more information is needed. It seems that GrapesJS is trying to delegate an event on the checkbox, but cannot find the element it should delegate to and keeps trying to retrieve the parentNode untill there is no parentNode anymore and the delegation target still isn't found.

Kind regards,

MetalPinguin