PropTypes error with addon-jest in latest beta

[mrmckeb]

PropTypes error with addon-jest in latest beta

Although it seems to work well, there is a PropType error in the console in the latest beta.

Steps to reproduce

• Install 4.0.0-alpha.23.
• Set up @storybook/addon-jest to use config file (addDecorator).
• Run Storybook.

The following error will appear in the browser console:
Warning: Failed prop type: Invalid prop `panels.storybook/tests/panel.title` supplied to `AddonPanel`.

Note that functionality is not impacted. Disabling the decorator resolves the issue.
// addDecorator(withTests({ results }));

Please specify which version of Storybook and optionally any affected addons that you're running

• @storybook/react 4.0.0-alpha.23
• @storybook/addon-jest 4.0.0-alpha.23

Screenshots

[mrmckeb]

I found the issue and I've created a PR to resolve this.