Material-ui: Tooltips broken in @material-ui/core": "^1.0.0-rc.1": A valid React element (or null) must be returned

[JohnPandich]

Upon rendering a Tooltip, the console shows: "Manager.render(): A valid React element (or null) must be returned. You may have returned undefined, an array or some other invalid object."

• [x ] I have searched the issues of this repository and believe that this is not a duplicate.

Expected Behavior

I expect the the Tooltip to render normally

Current Behavior

I see "Manager.render(): A valid React element (or null) must be returned. You may have returned undefined, an array or some other invalid object." when rendering the page

Steps to Reproduce (for bugs)

https://codesandbox.io/s/p9y18rlxmj

Context

We are developing a platform and can not release with this bug.

Your Environment

| Tech | Version |
|--------------|---------|
| Material-UI | 1.0.0-rc.1 |
| React | 15.6.2 |
| browser | chrome, firefox (probably all |
| etc | |

[janhoeck]

Your React version is your Problem. Update it to 16.3.2 on the sandbox and it will work.

[oliviertassinari]

@janhoeck Is correct. We only support React > 16.3.0 with v1.0.0-rc.0.
v1.0.0-beta.47 still support React 15.x.

[JohnPandich]

Thanks @janhoeck and @oliviertassinari ! Sorry for the extra effort