fix actions addon "cannot read count" error

[garrett-hopper]

I ran into this error when using the actions plugin on version 7.3.2

Specifically coming from addons/actions/src/manager.tsx#L13, where c would initially be undefined.

manager-bundle.js:150 Uncaught (in promise) TypeError: Cannot read properties of undefined (reading 'count')
    at manager-bundle.js:150:13268
    at Object.setAddonState (chunk-UBXIQABM.js:39:13762)
    at setState (chunk-UBXIQABM.js:53:35093)
    at chunk-UBXIQABM.js:53:36196
    at storybook/actions/action-event (manager-bundle.js:150:13248)
    at chunk-UBXIQABM.js:39:3795
    at Array.forEach (<anonymous>)
    at Channel.handleEvent (chunk-UBXIQABM.js:39:3779)
    at PostMessageTransport.<anonymous> (chunk-UBXIQABM.js:39:2430)
    at PostMessageTransport.handler (chunk-UBXIQABM.js:39:5469)

What I did

Added a optional chain and nullish coalesce to default count to 0

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[yannbf]

@kasperpeulen can you take a look? Seems like you worked on this as well

[kasperpeulen]

Might be solved with this PR:
#23804

[garrett-hopper]

Might be solved with this PR: #23804

Looks like it; closing

[ndelangen]

Thank you for contributing @garrett-hopper !
Sorry your PR wasn't able to be merged.