[OSD] Don't unset the icon when it hides

IconItem is now smart enough to not animate from the previous pixmap if it was hidden

shell/osd.cpp

@@ -174,6 +174,5 @@ void Osd::hideOsd()
     rootObject->setProperty("visible", false);
 
     // this is needed to prevent fading from "old" values when the OSD shows up
-    rootObject->setProperty("icon", "");
     rootObject->setProperty("osdValue", 0);
 }