* fix(util): guard BytesToUint{16,32,64} against short input
length is computed as uint, so length-1 on an empty slice underflows
to MaxUint and the loop indexes b[0] on a zero-length slice. BytesToUint16
also indexed b[0]/b[1] with no length check. All call sites today gate
the slice length explicitly, so this hardens the API for new callers
rather than fixing a live crash.
Return 0 on short input, matching the existing variable-length contract.
* BytesToUint16: match variable-length contract of the 32/64 helpers
A 1-byte slice should return uint16(b[0]) rather than 0, matching how
BytesToUint32 and BytesToUint64 treat short input.
65d557cbb0