Merge pull request #168 from jsor-labs/cancellation-queue-object-check

Backport "Add check whether $cancellable is an object" to 2.x

Author: clue

src/CancellationQueue.php

@@ -19,7 +19,7 @@ public function __invoke()
 
     public function enqueue($cancellable)
     {
-        if (!\method_exists($cancellable, 'then') || !\method_exists($cancellable, 'cancel')) {
+        if (!\is_object($cancellable) || !\method_exists($cancellable, 'then') || !\method_exists($cancellable, 'cancel')) {
             return;
         }