[Matter.framework] MTRAsyncWorkItem::initWithQueue will assert when the delayed scheduleSubscriptionPool fires after the deallocation of the MTRDevice (project-chip#35987)

Author: vivien-apple

src/darwin/Framework/CHIP/MTRDevice_Concrete.mm

@@ -1170,6 +1170,12 @@ - (void)_scheduleSubscriptionPoolWork:(dispatch_block_t)workBlock inNanoseconds:
     mtr_weakify(self);
     dispatch_block_t workBlockToQueue = ^{
         mtr_strongify(self);
+        if (nil == self) {
+            // This block may be delayed by a specified number of nanoseconds, potentially running after the device is deallocated.
+            // If so, MTRAsyncWorkItem::initWithQueue will assert on a nil queue, which will cause a crash.
+            return;
+        }
+
         // In the case where a resubscription triggering event happened and already established, running the work block should result in a no-op
         MTRAsyncWorkItem * workItem = [[MTRAsyncWorkItem alloc] initWithQueue:self.queue];
         [workItem setReadyHandler:^(id _Nonnull context, NSInteger retryCount, MTRAsyncWorkCompletionBlock _Nonnull completion) {