Test if this points to a liveUObject. This is an optimized version implying bEvenIfPendingKill=false, bThreadsafeTest=false. This should be done only when needed as excess resolution of the underlying pointer can cause performance issues. Note that IsValid can not be used on another thread as it will incorrectly return false during the mark phase of the GC due to the Unreachable flag being set. (see bThreadsafeTest above)