proofpoint_on_demand.mail: Fix script processor handling sm field

[kcreddy]

Proposed commit message

Fix null reference in script processor script_remove_unwanted_characters.

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.
• I have verified that any added dashboard complies with Kibana's Dashboard good practices

How to test this PR locally

Run pipeline tests:
eval "$(elastic-package stack shellinit)" && elastic-package test pipeline --generate -v --data-streams=mail

Before:

[0] unexpected pipeline error: [Processor script with tag script_remove_unwanted_characters in pipeline default-1733400250436322000 failed with message: cannot access method/field [to] from a null def reference]


╭──────────────────────┬─────────────┬───────────┬──────────────────────────────────────────┬─────────────────────────────────────────────────────────────────────────────┬──────────────╮
│ PACKAGE              │ DATA STREAM │ TEST TYPE │ TEST NAME                                │ RESULT                                                                      │ TIME ELAPSED │
├──────────────────────┼─────────────┼───────────┼──────────────────────────────────────────┼─────────────────────────────────────────────────────────────────────────────┼──────────────┤
│ proofpoint_on_demand │ mail        │ pipeline  │ (ingest pipeline warnings test-mail.log) │ PASS                                                                        │ 328.354709ms │
│ proofpoint_on_demand │ mail        │ pipeline  │ test-mail.log                            │ FAIL: test case failed: one or more problems with fields found in documents │ 699.680708ms │
╰──────────────────────┴─────────────┴───────────┴──────────────────────────────────────────┴─────────────────────────────────────────────────────────────────────────────┴──────────────╯
--- Test results for package: proofpoint_on_demand - END   ---
Done
Error: one or more test cases failed

Now:

--- Test results for package: proofpoint_on_demand - START ---
╭──────────────────────┬─────────────┬───────────┬──────────────────────────────────────────┬────────┬──────────────╮
│ PACKAGE              │ DATA STREAM │ TEST TYPE │ TEST NAME                                │ RESULT │ TIME ELAPSED │
├──────────────────────┼─────────────┼───────────┼──────────────────────────────────────────┼────────┼──────────────┤
│ proofpoint_on_demand │ mail        │ pipeline  │ (ingest pipeline warnings test-mail.log) │ PASS   │ 328.461625ms │
│ proofpoint_on_demand │ mail        │ pipeline  │ test-mail.log                            │ PASS   │ 158.642625ms │
╰──────────────────────┴─────────────┴───────────┴──────────────────────────────────────────┴────────┴──────────────╯
--- Test results for package: proofpoint_on_demand - END   ---
Done

[elasticmachine]

Pinging @elastic/security-service-integrations (Team:Security-Service Integrations)

[elastic-vault-github-plugin-prod]

🚀 Benchmarks report

To see the full report comment with /test benchmark fullreport

[elasticmachine]

💚 Build Succeeded

• Buildkite Build
• Commit: bdcd57dcdee23c0312c36a15efbd785ff685f177

cc @kcreddy

[elastic-sonarqube]

Quality Gate passed

Issues
0 New issues
0 Fixed issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube

[elastic-vault-github-plugin-prod]

Package proofpoint_on_demand - 1.0.2 containing this change is available at https://epr.elastic.co/package/proofpoint_on_demand/1.0.2/