Always crash when select Kindle 3 in Vector PDF

```
What steps will reproduce the problem?
1. Run PaperCrop
2. VectorPDF -> Kindle 3
3. Crash

What is the expected output? What do you see instead?


What version of the product are you using? On what operating system?
Windows 7. PaperCrop 0.51

Please provide any additional information below.


```

Original issue reported on code.google.com by `WeiExcel...@gmail.com` on 16 Jan 2013 at 9:41
