Exception when setting `selected` to invalid value, or removing all children

[michaelpg]

When in the course of human events it becomes necessary to remove the children of a core-animated-pages, an exception is thrown. This is the same behavior as when "selected" is set to an invalid value like -1 or undefined. I don't see this behavior in core-selector itself, though.

Exception caught during observer callback: TypeError: Cannot read property 'classList' of undefined
    at core-animated-pages.Polymer.applySelection
    at core-animated-pages.Polymer.mixin.selectedItemChanged
    at core-animated-pages.properties.invokeMethod
    at core-animated-pages.properties.notifyPropertyChanges
    at Object.Observer.report_
    at Object.createObject.check_

Is there any recourse or is core-animated-pages always supposed to have at least one page? I'm writing a component where pages can be added and removed dynamically.