[proofpoint_tap] Clean up null handling

[chrisberkhout]

Proposed commit message

[proofpoint_tap] Clean up null handling (#)

- Combine 'is null or not contains' checks.
- Combine 'not null and is/not value' checks.
- Remove redundant null-safe operator.

Checklist

• I have reviewed tips for building integrations and this pull request is aligned with them.
• I have verified that all data streams collect metrics or logs.
• I have added an entry to my package's changelog.yml file.
• I have verified that Kibana version constraints are current according to guidelines.

Related issues

• Relates Incorrect null handling in if conditions and elsewhere #8646

[elasticmachine]

🚀 Benchmarks report

Package proofpoint_tap 👍(0) 💚(3) 💔(1)

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Data stream	Previous EPS	New EPS	Diff (%)	Result
message_delivered	2923.98	2331	-592.98 (-20.28%)	💔

To see the full report comment with /test benchmark fullreport

[elasticmachine]

💚 Build Succeeded

• Buildkite Build
• Commit: c037d17

cc @chrisberkhout

[elastic-sonarqube]

Quality Gate passed

Kudos, no new issues were introduced!

0 New issues
0 Security Hotspots
90.5% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube

[elasticmachine]

Package proofpoint_tap - 1.16.3 containing this change is available at https://epr.elastic.co/search?package=proofpoint_tap