ffmpegdecoder/memorymanager: fixed race condition in garbage collection

app/codec/ffmpeg/ffmpegdecoder.h

@@ -64,9 +64,6 @@ public:
 
   virtual void Index(const QAtomicInt *cancelled) override;
 
-signals:
-  void ConsumedMemory();
-
 private:
   /**
    * @brief Handle an error
@@ -129,8 +126,6 @@ private:
 
   QTimer clear_timer_;
 
-  QAtomicInt allow_clear_event_;
-
 private slots:
   void FreeMemory();