fix: allow double update in scalar ignore nan implementation

[jvdd]

Fixes a bug in SCALAR<FloatIgnoreNaN> when the first element in the array is NaN.

The code used an else-if for updating low / max - but this should be 2 seperate ifs to allow double update when the first non-NaN value is encountered.

[codspeed-hq]

CodSpeed Performance Report

Merging #40 scalar_ignore_nan_bug (6ba2249) will not alter performances.

Summary

🔥 0 improvements
❌ 2 regressions
✅ 50 untouched benchmarks

🆕 0 new benchmarks
⁉️ 0 dropped benchmarks

Benchmarks breakdown

	Benchmark	main	scalar_ignore_nan_bug	Change
❌	scalar_f32_argminmax_in	1.7 ms	1.9 ms	-9.96%
❌	scalar_f64_argminmax_in	1.9 ms	2.1 ms	-9.02%