Fix incorrect field size for text fields The field size should be the string length excluding the terminating null byte which is there for convenience only when using the C API and not part of the on-disk format.

# try to opena file that specifies 0 iterations
$PWSDUMP -p "${TESTS_PATH}/password.txt" \
    "${TESTS_PATH}/invalid-iterations.psafe3"
grep 'invalid number of iterations: 0' "${LOGFILE}"