actions: toggle screen lock: check if screen is lockable before asking for width

src/sort_playlist.h

@@ -45,15 +45,13 @@ struct SortPlaylistDialog
 	virtual void spacePressed() OVERRIDE { }
 	virtual void mouseButtonPressed(MEVENT me) OVERRIDE;
 	
+	virtual bool isLockable() OVERRIDE { return false; }
 	virtual bool isMergable() OVERRIDE { return false; }
 	
 	// private members
 	void moveSortOrderUp();
 	void moveSortOrderDown();
 	
-protected:
-	virtual bool isLockable() OVERRIDE { return false; }
-	
 private:
 	void moveSortOrderHint() const;
 	void sort() const;