Merge branch '5.2' into 5.x

* 5.2:
  [CS] Replace easy occurences of ?: with ??

Author: derrabus

Tests/Transport/AmqpTransportTest.php

@@ -54,8 +54,8 @@ public function testReceivesMessages()
 
     private function getTransport(SerializerInterface $serializer = null, Connection $connection = null): AmqpTransport
     {
-        $serializer = $serializer ?: $this->createMock(SerializerInterface::class);
-        $connection = $connection ?: $this->createMock(Connection::class);
+        $serializer = $serializer ?? $this->createMock(SerializerInterface::class);
+        $connection = $connection ?? $this->createMock(Connection::class);
 
         return new AmqpTransport($connection, $serializer);
     }