Fix SocketIpcHub::accept if already cancelled

Relates to #199.

src/Ipc/SocketIpcHub.php

@@ -165,9 +165,10 @@ public function accept(string $key, ?Cancellation $cancellation = null): Resourc
             $this->queued = true;
         }
 
-        $this->waitingByKey[$key] = $suspension = EventLoop::getSuspension();
-
         $cancellation = $cancellation ?? new NullCancellation();
+        $cancellation->throwIfRequested();
+
+        $this->waitingByKey[$key] = $suspension = EventLoop::getSuspension();
         $cancellationId = $cancellation->subscribe(function (CancelledException $exception) use ($suspension) {
             $suspension->throw($exception);
         });