fix(idempotency): add null check for idempotencyHandler before calling handleMiddyOnError

[mdesousa]

Summary

Fixes #4634

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[boring-cyborg]

Thanks a lot for your first contribution! Please check out our contributing guidelines and don't hesitate to ask whatever you need.
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[svozza]

Thanks for the PR. Can you add the acknowledgement text into your issue, just paste it at the bottom:

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

Disclaimer: We value your time and bandwidth. As such, any pull requests created on non-triaged issues might not be successful.

Also, is there a way to have a unit test for when the value is null/undefined. Would be nice to be able to guard against regressions here for a bug that causes a runtime exception.

[mdesousa]

hi @svozza unit test and disclamer added 👍

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[svozza]

LGTM. Thanks a lot!

[boring-cyborg]

Awesome work, congrats on your first merged pull request and thank you for helping improve everyone's experience!