RFR: 8203499 Uninitialised memory in WinAccessBridge.cpp

[Phil Race]

Bug: Uninitialised memory in WinAccessBridge.cpp:485
webrev: http://cr.openjdk.java.net/~prr/8203499/
element is not initialised on declaration.

It should be initialised when its address is passed here
messageQueue->remove(&element);

but it is too hard to prove, so just initialise it to NULL .. and remove 
DEBUG code which will SEGV if it is NULL.

-phil.