fix(bigquery): prevent NullPointerException in OTel tracing when JobId is null

[keshavdandeva]

b/517929704

This PR addresses a NullPointerException that occurs in the BigQuery client library when OpenTelemetry tracing is enabled and operations are performed on jobs that do not have a client-assigned JobId at the start of the call.

A notable case where this happens is during dry-run queries (often used to determine statement type or fetch statistics) where JobInfo.getJobId() returns null. The OTel instrumentation was attempting to extract attributes from the JobId without checking for nullability.

Changes:

• Added null checks before calling JobId.getOtelAttributes() in BigQueryImpl.create(JobInfo) (line 455).
• Added null checks before calling JobId.getOtelAttributes() in BigQueryImpl.getQueryResults(JobId) (line 2128).
• These changes align with the safe-check pattern already implemented in BigQueryImpl.queryWithTimeout (line 2075).

[gemini-code-assist]

Code Review

This pull request adds null checks for job IDs before retrieving OpenTelemetry attributes in BigQueryImpl.java. The reviewer recommended using Attributes.empty() instead of passing null to setAllAttributes to prevent potential NullPointerExceptions in certain OpenTelemetry implementations or mock tracers.

[lqiu96]

Thanks for the info and the context. I don't have any concerns with this