Merge branch '7.2' into 7.3

* 7.2:
  return early if handle has been cleaned up before

Author: xabbuh

Response/AmpResponseV5.php

@@ -240,6 +240,10 @@ private static function generateResponse(Request $request, AmpClientStateV5 $mul
             $body = $response->getBody();
 
             while (true) {
+                if (!isset($multi->openHandles[$id])) {
+                    return;
+                }
+
                 $multi->openHandles[$id]->complete();
                 $multi->openHandles[$id] = new DeferredFuture();