fix(rest): improves error handling for express middleware

[raymondfeng]

Fixes #4530

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• npm test passes on your machine
• New tests added or existing tests modified to cover all changes
• Code conforms with the style guide
• API Documentation in code was updated
• Documentation in /docs/site was updated
• Affected artifact templates in packages/cli were updated
• Affected example projects in examples/* were updated

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[bajtos]

Thank you for opening a PR to fix the crash. I have different opinions on how to fix the problem, please see my comments below.

[raymondfeng]

@bajtos PTAL.

[bajtos]

The new proposal looks much better now 👍

Can you please clean up the code a bit per my comment below?

I am also a bit concerned that by invoking the new error handler also for errors leaked by the sequence, we may end up with calling reject two times:

1. First, we call reject from the sequence. Something unexpected happens and an error is thrown.
2. Then we call reject again from the last-resort error handler.

Maybe this is not a problem? IDK.

[raymondfeng]

I am also a bit concerned that by invoking the new error handler also for errors leaked by the sequence, we may end up with calling reject two times:
First, we call reject from the sequence. Something unexpected happens and an error is thrown.
Then we call reject again from the last-resort error handler.

Good question. I think it's a rare edge case and probably not too bad to call it twice.