normalizeNode doesn't call next()

[matejlauko]

normalizeNode middleware in the plugin doesn't call next(), so it doesn't call any other normalizeNodes in the next plugins.

viz https://github.com/ianstormtaylor/slate/blob/master/packages/slate/Changelog.md#0420--october-9-2018 -> "The middleware stack is now deferrable"

[omar-sr88]

Is this issue still open?

These commits to have fixed it

89f2313#diff-77a69f8b520ea5326dc78d38cf82a957

be1e85b#diff-77a69f8b520ea5326dc78d38cf82a957