Fix build

Signed-off-by: falkTX <falktx@falktx.com>

source/backend/engine/CarlaEngineJack.cpp

@@ -1781,7 +1781,7 @@ public:
     void idle() noexcept override
     {
         LinkedList<PostPonedJackEvent> events;
-        PostPonedJackEvent nullEvent = {};
+        const PostPonedJackEvent nullEvent = {};
 
         {
             const CarlaMutexLocker cml(fPostPonedEventsMutex);
@@ -1802,9 +1802,6 @@ public:
             case PostPonedJackEvent::kTypeClientUnregister:
                 handleJackClientUnregistrationCallback(ev.clientUnregister.name);
                 break;
-            case PostPonedJackEvent::kTypeClientUnregister:
-                handleJackClientUnregistrationCallback(ev.clientUnregister.name);
-                break;
             case PostPonedJackEvent::kTypePortRegister:
                 handleJackPortRegistrationCallback(ev.portRegister.fullName,
                                                    ev.portRegister.shortName,