ntdll: Duplicate handles for thread pool waits.
Windows allows closure of a waitable timer handle while a work item is waiting on it. Also, the current Wine ntdll implementation calls NtWaitForMultipleObjects() on multiple handles if multiple items are pending, and if one handle is not valid, no items will execute.
Btw there are occurrences of INVALID_HANDLE_VALUE
elsewhere, e.g. in RtlDeleteTimer()
, which I think are incorrect, unless Windows internals are inconsistent with its use.