Fix continous crash in WindowManager in boot

Bug: 28728894
Change-Id: I660e2709a674eb4089dbb38173375491a87828db
diff --git a/services/core/java/com/android/server/policy/PhoneWindowManager.java b/services/core/java/com/android/server/policy/PhoneWindowManager.java
index 0a5b82a..b2cf89b 100644
--- a/services/core/java/com/android/server/policy/PhoneWindowManager.java
+++ b/services/core/java/com/android/server/policy/PhoneWindowManager.java
@@ -3957,7 +3957,7 @@
             if (!isKeyguardShowing) {
                 navTranslucent &= areTranslucentBarsAllowed();
             }
-            boolean statusBarExpandedNotKeyguard = !isKeyguardShowing
+            boolean statusBarExpandedNotKeyguard = !isKeyguardShowing && mStatusBar != null
                     && mStatusBar.getAttrs().height == MATCH_PARENT
                     && mStatusBar.getAttrs().width == MATCH_PARENT;