(Closes #7) fix when privateKeyExtended when privateKey is null

lib/hdkey.js

@@ -57,7 +57,8 @@ Object.defineProperty(HDKey.prototype, 'publicKey', {
 
 Object.defineProperty(HDKey.prototype, 'privateExtendedKey', {
   get: function () {
-    return cs.encode(serialize(this, this.versions.private, Buffer.concat([new Buffer([0]), this.privateKey])))
+    if (this._privateKey) return cs.encode(serialize(this, this.versions.private, Buffer.concat([new Buffer([0]), this.privateKey])))
+    else return null
   }
 })
 

test/hdkey.test.js

@@ -139,4 +139,20 @@ describe('hdkey', function () {
       assert(HDKey.HARDENED_OFFSET)
     })
   })
+
+  describe('> when private key is null', function () {
+    it('privateExtendedKey should return null and not throw', function () {
+      var seed = '000102030405060708090a0b0c0d0e0f'
+      var masterKey = HDKey.fromMasterSeed(new Buffer(seed, 'hex'))
+
+      assert.ok(masterKey.privateExtendedKey, 'xpriv is truthy')
+      masterKey._privateKey = null
+
+      assert.doesNotThrow(function () {
+        masterKey.privateExtendedKey
+      })
+
+      assert.ok(!masterKey.privateExtendedKey, 'xpriv is falsy')
+    })
+  })
 })