Request for reviews (XS): 6880052

[Vladimir Kozlov]

http://cr.openjdk.java.net/~kvn/6880052/webrev.00

Fixed 6880052: SIGSEGV in GraphKit::null_check_common()

Problem:
After 6875577 fix the method do_null_check() checks for
unloaded klass also for arrays. But array type may not
have klass, for example, when element type is Bottom.
The bug case has Phi node which merges several CheckCastPP
with different types so its type is bottom[int:>=0].

Solution:
Check that a klass is not NULL before the unloaded check.

Reviewed by:

Fix verified (y/n): y, test

Other testing:
JPRT