RFR: 8230398: Remove NULL checks before FREE_C_HEAP_ARRAY

[Leo Korinth]

Hi!

This fixup removes NULL checks before FREE_C_HEAP_ARRAY. This is 
unnecessary as FREE_C_HEAP_ARRAY does also do this NULL check. This is a 
follow up to 8227168: Cleanup usage of NEW_C_HEAP_ARRAY.

deallocate_counters() in src/hotspot/os/windows/os_perf_windows.cpp does 
(in addition to NULL the pointer) also set a counter to zero. Although 
my change "looks" correct, I tried follow the usage of 
deallocate_counters(), and could not find a call site. Should I create a 
bug on this, or am I missing something here?

Bug:
https://bugs.openjdk.java.net/browse/JDK-8230398

Webrev:
http://cr.openjdk.java.net/~lkorinth/8230398

Testing:
mach5 tier1-3

Thanks,
Leo