handle a case where the record is some customized item

[joeyzhao2018]

What does this PR do?

https://datadoghq.atlassian.net/browse/SLES-2218
The customer is using some customized event payload and hitting some corner cases.
This is the minimal change needed to support their customized payloads.

I will create another PR to add more type checks, which will need performance check.

Motivation

Testing Guidelines

Additional Notes

Types of Changes

• Bug fix
• New feature
• Breaking change
• Misc (docs, refactoring, dependency upgrade, etc.)

Check all that apply

• This PR's description is comprehensive
• This PR contains breaking changes that are documented in the description
• This PR introduces new APIs or parameters that are documented and unlikely to change in the foreseeable future
• This PR impacts documentation, and it has been updated (or a ticket has been logged)
• This PR's changes are covered by the automated tests
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