test(matrix): test Matrix::is_empty()

[codspeed-hq[bot]]

CodSpeed Performance Report

Merging #567 will degrade performances by 10.82%

_{Comparing add-tests (9116e1c) with main (eafb4d6)}

Summary

❌ 1 regressions ✅ 33 untouched benchmarks

:warning: Please fix the performance issues or acknowledge them on CodSpeed.

Benchmarks breakdown

	Benchmark	main	add-tests	Change
❌	separate_components	1.9 ms	2.1 ms	-10.82%