Prevent nil receipts and added retry logic for making chain events

[jeongkyun-oh]

Proposed changes

Making a chain event is done locally after getting items from database. It was hard to get an error, but the error case is not handled properly. This change checks if receipt list is nil or not, and added retrying logic for making chain events.

Unlike retrying to produce Kafka messages, it should not fail to get data from the database. It retries inifinately, but after 100 retry it leaves error logs.

Types of changes

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• Bugfix
• New feature or enhancement
• Others

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[hyochan-brown]

LGTM!!
I have only one question.

[KimKyungup]

@jeongkyun-oh What is the root cause of not having a receipt?

[jeongkyun-oh]

@KimKyungup Unexpected errors occur in DynamoDB unlike LevelDB. The retry logic is added for unexpected temporary errors.

[jeongkyun-oh]

Dear reviewers, sorry for confusion.

For now, #982 PR fixes the current issue.
For retry, I will make another PR in the near future.
I made another PR for checking nil receipts in #983.