Fixed NPE during boot animation on fugu.

- Don't set a dim layer in the docked controller if we are not dimming.
- Check to make sure the docked divider window isn't null before trying
to use its layer for dimming.

Bug: 28339915
Change-Id: I33d49d26ffcaec63d135f82a6208e127ba0f0570
diff --git a/services/core/java/com/android/server/wm/DockedStackDividerController.java b/services/core/java/com/android/server/wm/DockedStackDividerController.java
index 30ba28a..8174c13 100644
--- a/services/core/java/com/android/server/wm/DockedStackDividerController.java
+++ b/services/core/java/com/android/server/wm/DockedStackDividerController.java
@@ -538,12 +538,15 @@
     }
 
     public boolean animate(long now) {
+        if (mWindow == null) {
+            return false;
+        }
         if (mAnimatingForMinimizedDockedStack) {
             return animateForMinimizedDockedStack(now);
         } else if (mAnimatingForIme) {
             return animateForIme(now);
         } else {
-            if (mDimLayer != null) {
+            if (mDimLayer != null && mDimLayer.isDimming()) {
                 mDimLayer.setLayer(mService.mLayersController.getResizeDimLayer());
             }
             return false;