Addon-contexts: Ensure nodes be an array
Addon-contexts: Ensure nodes be an array

* Fix rendering crash when user navigates to non-Canvas tab to Canvas
  tab (#7324).

storybooks/react-storybook,kadirahq/react-storybook,storybooks/storybook,storybooks/react-storybook,kadirahq/react-storybook,storybooks/storybook,storybooks/storybook,storybooks/storybook,storybooks/storybook,storybooks/storybook,storybooks/storybook,storybooks/react-storybook,storybooks/react-storybook