Default schema normalization infinite loop

[tommoor]

Do you want to request a feature or report a bug?

Bug

What's the current behavior?

In the latest versions of Slate nested marks when the schema specifies marks: [''] results in an infinite loop attempting to normalize. See JSFiddle reproducing the issue here:

https://jsfiddle.net/fj9dvhom/20/

Screenshot of stack:

What's the expected behavior?

The expected behavior is that the node would have all marks removed. Perhaps there is a better way of specifying that a node should only be plain text with no children or marks? If that's the case I'd be happy to put in a PR improving the docs on this usecase 😄

[ianstormtaylor]

Fixed by #3093.