Editor doesn't work when using Symbol polyfil

[dovydaskukalis]

📝 Provide detailed reproduction steps (if any)

Due to this issue babel/babel#6010, the editor fails to initiate because this always returns true even when it shouldn't. Another piece of code with the same issue is here. Changing observablePropertiesSymbol in this to this[observablePropertiesSymbol] and observablePropertiesSymbol in observable to observable[observablePropertiesSymbol] makes the editor work fine.

I am aware it only supports modern browsers however without these changes it does not work on mobile apps built with Meteor or any other tool that adds this polyfil. As it's a simple fix, please consider making these changes 🙂

✔️ Expected result

Editor works with Symbol polyfil.

❌ Actual result

Editor doesn't load at all.

[Reinmar]

Hi! Thanks for a detailed issue report. If the mentioned change solves the issue, then I think we'll be fine with it. Could you make a PR perhaps?

[dovydaskukalis]

Sure, will do.