Treat blank preRelease the same as null?

[peterfigure]

SemVer(1, 2, 3).copy(preRelease = "") will throw an Exception.. seems a bit unreasonable?

how about

if (!preRelease.isNullOrBlank()) require(preRelease.matches(Regex("""[\dA-z\-]+(?:\.[\dA-z\-]+)*"""))) { "Pre-release version is not valid" }