effects/fullscreen: Prevent playing animation for invisible windows

It makes no sense to play the animation if the window is invisible. It
can also produce unexpected results if the window is not on current virtual
desktop as animate() will temporarily force the window to be visible.

src/effects/fullscreen/package/contents/code/fullscreen.js

@@ -25,7 +25,7 @@ class FullScreenEffect {
     }
 
     onWindowFullScreenChanged(window) {
-        if (!window.oldGeometry) {
+        if (!window.visible || !window.oldGeometry) {
             return;
         }
         window.setData(Effect.WindowForceBlurRole, true);