[PWGLF] Fix place of histogram filling

[gbencedi]

No description provided.

[github-actions]

O2 linter results: ❌ 0 errors, ⚠️ 0 warnings, 🔕 0 disabled

[alibuild]

Auto-approving on behalf of @gbencedi.

[alibuild]

Error while checking build/O2Physics/code-check for c605e70 at 2026-08-01 10:08:

## sw/BUILD/O2Physics-code-check-latest/log
--
========== List of issues found ==========
++ echo 'Found 3 errors and 0 warnings.'
Found 3 errors and 0 warnings.
++ [[ 3 -gt 0 ]]
++ cat /sw/BUILD/2da66c14b6d2f24fd5f19d79f2c1c2ecf2cfbfde/O2Physics-code-check/errors.txt
PWGLF/Tasks/GlobalEventProperties/flattenictyPikp.cxx:1902:45: error: repeated branch body in conditional chain [bugprone-branch-clone,-warnings-as-errors]
PWGLF/Tasks/GlobalEventProperties/flattenictyPikp.cxx:1908:45: error: repeated branch body in conditional chain [bugprone-branch-clone,-warnings-as-errors]
PWGLF/Tasks/GlobalEventProperties/flattenictyPikp.cxx:1914:46: error: repeated branch body in conditional chain [bugprone-branch-clone,-warnings-as-errors]
++ [[ 0 -gt 0 ]]
++ [[ 3 -gt 0 ]]
++ exit 1
--

Full log here.