strtoul calls not handled properly

[pacu]

from man strtoul

RETURN VALUES
The strtoul(), strtoull(), strtoumax() and strtouq() functions return
either the result of the conversion or, if there was a leading minus
sign, the negation of the result of the conversion, unless the original
(non-negated) value would overflow; in the latter case, strtoul() returns
ULONG_MAX, strtoull() returns ULLONG_MAX, strtoumax() returns
UINTMAX_MAX, and strtouq() returns ULLONG_MAX. In all cases, errno is
set to ERANGE. If no conversion could be performed, 0 is returned and
the global variable errno is set to EINVAL (the last feature is not por-
table across all platforms).

strtoul function returns values on error which are taken as valid inputs and carried over to the result of the function call

MnemonicKit/MnemonicKit/String+MnemonicData.swift

Line 5 in caf90cd

public extension String {

public extension String {
  func mnemonicData() -> Data {
    let length = self.count
    let dataLength = length / 2
    var dataToReturn = Data(capacity: dataLength)

    var outIndex = 0
    var outChars = ""
    for (_, char) in enumerated() {
      outChars += String(char)
      if outIndex % 2 == 1 {
        let i: UInt8 = UInt8(strtoul(outChars, nil, 16))
        dataToReturn.append(i)
        outChars = ""
      }
      outIndex += 1
    }

    return dataToReturn
  }
}

• solution *
  Use Int(outChars, radix: 16) instead and care for nil value