Deriving public keys fails when given an xpub key

[thallium205]

Given an xpub key, one should be able to generate derived public keys from it in a simple m/i derivation path as done on http://bip32.org/. However, when trying to do so, a BigDecimal exception is thrown.

How to reproduce:

var bitcoin = require('bitcoinjs-lib');
new bitcoin.HDWallet.fromBase58('xpub6CxuB8ifZCMXeS3KbyNkYvrsJEHqxedCSiUhrNwH1nKtb8hcJpxDbDxkdoVCTR2bQ1G8hY4UMv85gef9SEpgFFUftBjt37FUSZxVx4AU9Qh').derive(0);

Error:

TypeError: Object (55066263022277343669578718895168534326250603453777594175500187360389116729240,32670510020758816978083085130507043184471273380659243275938904335757337482424) has no method 'abs'

[dcousens]

I'll be investigating this, thanks.