Use context to get active device

An event made with a native handle will not have an initialized queue. So it is better
to get the scoped context device through the context, which is always guaranteed to
be initialized.

source/adapters/hip/event.cpp

@@ -190,7 +190,7 @@ urEventWait(uint32_t numEvents, const ur_event_handle_t *phEventWaitList) {
   UR_ASSERT(numEvents > 0, UR_RESULT_ERROR_INVALID_VALUE);
 
   try {
-    ScopedContext Active(phEventWaitList[0]->getDevice());
+    ScopedContext Active(phEventWaitList[0]->getContext()->getDevices()[0]);
     auto WaitFunc = [](ur_event_handle_t Event) -> ur_result_t {
       UR_ASSERT(Event, UR_RESULT_ERROR_INVALID_EVENT);