isValidMatter

Returns this CMatter is a valid or not.

CMatter's default implementation checks below conditions.

• CMatter.candidate is not empty

• CMatter.candidate does not contain Material.isAir and !Material.isItem

• CMatter.amount is 1 or more

// (Usage)
val matter: CMatter = ~~~
matter.isValidMatter().exceptionOrNull()?.let { throw it }

This is called from CRecipe.isValidRecipe.