UndoButton/RedoButton cannot be initialized before Editor

Hi,

I’m writing a toolbar with DraftJS, and it will be rendered before the Editor.

<div>
<Toolbar><RedoButton/><UndoButton/></Toolbar>
<Editor .../>
</div>

I think it’s because the RedoButton/UndoButton didn’t consider the situation that the Editor has not been initialized before the buttons are rendered.

Uncaught TypeError: this.props.store.getEditorState is not a function
    at UndoButton.render (index.js:59)
    at ReactCompositeComponent.js:796
    at measureLifeCyclePerf (ReactCompositeComponent.js:75)
    at ReactCompositeComponentWrapper._renderValidatedComponentWithoutOwnerOrContext 

Exception line: https://github.com/draft-js-plugins/draft-js-plugins/blob/master/draft-js-undo-plugin/src/RedoButton/index.js#L21

When the method “getEditorState” is actually initialized: https://github.com/draft-js-plugins/draft-js-plugins/blob/master/draft-js-undo-plugin/src/index.js#L30

[Hongbo-Miao]

I think this also happens to LinkButton. Got same error if editor is not ready.

[stale[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.