Fix message queue issues

- Missing flush in resource loading.
- Wrong checks about message queue instance.

core/object/message_queue.h

@@ -40,6 +40,8 @@
 class Object;
 
 class CallQueue {
+	friend class MessageQueue;
+
 public:
 	enum {
 		PAGE_SIZE_BYTES = 4096
@@ -75,6 +77,10 @@ private:
 	uint32_t pages_used = 0;
 	bool flushing = false;
 
+#ifdef DEV_ENABLED
+	bool is_current_thread_override = false;
+#endif
+
 	struct Message {
 		Callable callable;
 		int16_t type;