NullPointerException while signing with a BKS keystore

[GoogleCodeExporter]

- What steps will reproduce the problem?
1. create a new BKS keystore (with .bks extension)
2. sign an unsigned APK with a key from that keystore
3. A toast with "null" is displayed

- What is the expected output? What do you see instead?
(empty)

- What version of the product are you using? On what operating system?
ZipSigner 3.4 from the the play store
Android 4.2.2 on a Galaxy Nexus

- Please provide any additional information below.
I first got the exception in a little program I am developing. The exception is 
thrown on ZipSigner.signZip()[line 709]. I tested on the Android App available 
on the Play Store and it has the same issue. I succeeded to sing the APK with a 
JKS keystore though.

PS: thanks for such a powerful library!

Original issue reported on code.google.com by [email protected] on 20 Jun 2013 at 12:41