Local storage quota exceeded can crash editor

When opening Gutenberg in private browsing in Firefox, the local storage quota is much lower than usual. This can lead to the quota easily being exceeded.

In our [editor settings override code](https://github.com/humanmade/altis-cms/blob/master/assets/editor-settings.js), we override Gutenberg's settings. It's easily possible for this to hit and exceed the quota thanks to Pinpoint's use of local storage as well, and this throws a quota exception. The exception acts as an uncaught exception which then crashes Gutenberg into an unrecoverable state.

We need to catch these exceptions inside `updateSettings`.