Wrap adding to fading out

needed to avoid memory safety issues, because sometimes there would be duplicates.

src/Compositor.hpp

@@ -146,6 +146,8 @@ public:
     void                    moveUnmanagedX11ToWindows(CWindow*);
     CWindow*                getX11Parent(CWindow*);
     void                    scheduleFrameForMonitor(SMonitor*);
+    void                    addToFadingOutSafe(SLayerSurface*);
+    void                    addToFadingOutSafe(CWindow*);
 
     std::string             explicitConfigPath;