fix startTransition inside renderers when _callbacks is undefined

[sync]

Summary:

When using startTransition using latest react-native (0.74.1, new arch enabled) we get this error:

TypeError: Cannot read property 'add' of undefined

You can easily reproduce this issue creating a new react-native app (latest) and add a transition and execute it.

Sample app here: https://github.com/sync/Shift

Changelog:

[GENERAL] [FIXED] - fixed startTransition inside renderers when _callbacks is undefined

Test Plan:

Before

After

all good with the patch: sync/Shift#1

[brentvatne]

these files are synced from react and shouldn't be modified directly here.

ideally, we'd create a minimal repro with react-native (without any third-party dependencies) and post it on an issue here. or, if you believe you know what is causing this in react, you could create an issue on react with a repro or a pr with a failing test that demonstrates it

[sync]

Thanks for having a look @brentvatne, have a minimal repo here: https://github.com/sync/Shift

[sync]

I’ll have a look at the original files and see if anything changed in between versions

[sync]

so yes the code is brand new (from 2 months ago) and was added in this commit: 3272b05

[sync]

Code on the react repo that introduced this is very recent: acdlite/react@85b296e and master no longer have this code (it was removed here: acdlite/react@12a387d)