pipeline: inputs: podman_metrics: use after free fix

[mabrarov]

pipeline: inputs: podman_metrics: fixed use after free which was discovered by failed CI build (after migration from GCC 7 to GCC 9 in #10230 which was merged as part of #10178) with optimization for size turned on (cmake -DFLB_SMALL=On ...).

Refer to https://github.com/fluent/fluent-bit/actions/runs/14581214135/job/40898148724?pr=7608 for the issue which this pull request fixes.

---

Testing

• [N/A] Example configuration file for the change
• [N/A] Debug log output from testing the change
• Attached Valgrind output that shows no leaks or memory corruption was found - refer to flb_run_code_analysis_10234.log for the output of command

  TEST_PRESET=valgrind SKIP_TESTS='flb-rt-out_td flb-it-network' ./run_code_analysis.sh

• [N/A] Run local packaging test showing all targets (including any new ones) build.
• [N/A] Set ok-package-test label to test for all targets (requires maintainer to do).

Documentation

• [N/A] Documentation required for this feature

Backporting

• [N/A] Backport to latest stable release.

---

Fluent Bit is licensed under Apache 2.0, by submitting this pull request I understand that this code will be released under the terms of that license.