Code review request: 8008071: Crashed in promote_malloc_records() with Kitchensink after 19 days

[Zhengyu Gu]

This is a simple fix to add NULL pointer check. This bug is hard to 
reproduce, since it only happens what an arena pointer has highest 
address in NMT database.


Bug: http://bugs.sun.com/view_bug.do?bug_id=8008071
Webrev: http://cr.openjdk.java.net/~zgu/8008071/webrev.00/

Test:

I have Kitchensink running over a day now, still in progress.


Thanks,

-Zhengyu