fix(ddtrace/tracer): fix panic in SQLCommentCarrier

[rarguelloF]

What does this PR do?

Fixes #2837

Motivation

Reviewer's Checklist

• Changed code has unit tests for its functionality at or near 100% coverage.
• System-Tests covering this feature have been added and enabled with the va.b.c-dev version tag.
• There is a benchmark for any new code, or changes to existing code.
• If this interacts with the agent in a new way, a system test has been added.
• Add an appropriate team label so this PR gets put in the right place for the release notes.
• Non-trivial go.mod changes, e.g. adding new modules, are reviewed by @DataDog/dd-trace-go-guild.
• For internal contributors, a matching PR should be created to the v2-dev branch and reviewed by @DataDog/apm-go.

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[datadog-datadog-prod-us1]

Datadog Report

Branch report: rarguelloF/fix-sqlcomment-panic
Commit report: 72af291
Test service: dd-trace-go

✅ 0 Failed, 5122 Passed, 70 Skipped, 2m 35.38s Total Time

[pr-commenter]

Benchmarks

Benchmark execution time: 2025-01-09 13:23:34

Comparing candidate commit 5bba578 in PR branch rarguelloF/fix-sqlcomment-panic with baseline commit 4f57a47 in branch main.

Found 3 performance improvements and 0 performance regressions! Performance is the same for 56 metrics, 0 unstable metrics.

scenario:BenchmarkSetTagString-24

• 🟩 execution_time [-12.200ns; -10.060ns] or [-9.886%; -8.151%]

scenario:BenchmarkSetTagStringer-24

• 🟩 execution_time [-11.379ns; -8.241ns] or [-7.471%; -5.410%]

scenario:BenchmarkTracerAddSpans-24

• 🟩 execution_time [-238.013ns; -192.587ns] or [-5.797%; -4.691%]