Fix bug 6596440: NPE when pulling down notification window

Pulling down the notification window set the navigation bar view to
"slippery", but this view is NULL on some devices such as Crespo.
The fix simply makes it a no-op in this case.

Change-Id: I720a257c1715febda5932d50906c5dddbca2b312

Author: raphlinus

packages/SystemUI/src/com/android/systemui/statusbar/phone/PhoneStatusBar.java

@@ -1054,6 +1054,9 @@ private void makeExpandedVisible() {
     }
 
     private static void makeSlippery(View view, boolean slippery) {
+        if (view == null) {
+            return;
+        }
         WindowManager.LayoutParams lp = (WindowManager.LayoutParams) view.getLayoutParams();
         if (slippery) {
             lp.flags |= WindowManager.LayoutParams.FLAG_SLIPPERY;