Bug: useFormState formAction becomes null in strict mode

[akmtagline]

The form action returned from the hook useFormState becomes null when using React strict mode. It causes the page to reload on the submission of the form and the action does not work. I know that the React strict mode performs some actions twice intentionally to find unexpected behavior in the development. But, it would be better if we could use it without disabling the Strict mode.

React version: 0.0.0-experimental-bb0944fe5-20240313

Steps To Reproduce

1. Enable strict mode
2. Submit the form that uses form action returned from useFormState

Link to code example:
https://codesandbox.io/p/sandbox/jolly-minsky-kmkspd
https://codesandbox.io/p/sandbox/damp-tree-yv2vzy

The current behavior

Form action becomes null causing the page to reload.

The expected behavior

Form action should be a function provided as the argument in the useFormState hook.

[eps1lon]

I simplified the repro to a single file since the use server; directive has no effect in CodeSandbox: https://codesandbox.io/p/sandbox/useformstate-strictmode-double-invoke-action-nulled-6ltttr

18.3.0-canary-bb0944fe5-20240313: bad
18.3.0-canary-b36ae8d7a-20231207: good
18.3.0-canary-971b62f47-20240129: good
18.3.0-canary-2e470a788-20240214: good
18.3.0-canary-01ab35a9a-20240228: good
18.3.0-canary-0066e0b68-20240306: good
18.3.0-canary-eb33bd747-20240312: good

Last good: 18.3.0-canary-eb33bd747-20240312
First bad: 18.3.0-canary-bb0944fe5-20240313

New changes in 18.3.0-canary-bb0944fe5-20240313: eb33bd7...bb0944f

Looks like #28514 broke this.