PerfMonComps: Add protection against division by zero
This fixes the crash reported in ATLASRECTS-6605 from a technical point of view (we shouldn't crash under any circumstance). The actual metrics are still missing even after this MR but that seems to be "incidentally" fixed by !47091 (merged). I'm starting to think maybe we should move PerfMonMTAlg
back to the standard algorithm sequence, i.e. revert !47011 (merged).