Atmosphere/atmosphere — pull request #661 by sjardine (2012-10-02 23:09:08+00:00)
Title: Possible NumberFormatException when HttpSession#getAttribute returns null.

When using SessionBroadcasterCache I get an exception when calling Broadcaster#addResource. The exception is generated when calling:
```java
Long.valueof((String)session.getAttribute(broadcasterId));
```
For me the HttpSession#getAttribute call returns null so I added a null check.

I am not sure if this is all that it needed but the build compiles without error and as far as I can tell the problem is fixed for me.