Failed prop type: Invalid prop `flip` of value `null`

[nipponvn0803]

Describe the bug
The flip prop has null as default value, here.
but it does not accept null as a valid value, here.

Reproducible test case
CodeSandbox link
Clicking the flip button will show an error in console.

Expected behavior
It should accept null as a valid value and not show any error.

Desktop (please complete the following information):

• Browser: Chrome
• Version: 85.0.4183.102 (Official Build) (64-bit)

Additional context
None

[charles4221]

Fixed as of #581 (3.0.0)