Align reads to Null_Region   

```
We experience that a very small amount of reads are aligned to sequence name 
"Null region". This means PerM couldn't find the "sequence name" that the read 
aligned to. Currently, those alignment are suggested to be ignored.


```

Original issue reported on code.google.com by `Chen.Yan...@gmail.com` on 6 Aug 2011 at 3:32
