fix: do not error out if no head report is present after local run

[GuillaumeLagrange]

This used to happen on local runs with integration when no run on main branch is present.

[codspeed-hq]

Merging this PR will not alter performance

✅ 4 untouched benchmarks

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_{Comparing cod-2175-first-local-run-inside-a-repo-not-linked-to-codspeed-gets (ad9d1dc) with main (920c7a1)}