Recover test for pfr get_row_name_table with empty structs

[This check](https://github.com/boostorg/mysql/blob/90405e79e4590f142e28094eea1625f259ffeec4/test/unit/test/pfr.cpp) fails under recent versions of AppleClang (see [this build](https://github.com/boostorg/mysql/actions/runs/15423871327/job/43405774053?pr=480)). Understand why and report any potential problem to PFR.
