Fix NPE in SyncManager

Bug: 2660742
Change-Id: I80ec62a0e128b3f20873a718d951e41f3fa2eb90
diff --git a/src/com/android/exchange/SyncManager.java b/src/com/android/exchange/SyncManager.java
index b451ef1..8059425 100644
--- a/src/com/android/exchange/SyncManager.java
+++ b/src/com/android/exchange/SyncManager.java
@@ -830,8 +830,10 @@
 
     static public String getEasAccountSelector() {
         SyncManager syncManager = INSTANCE;
-        if (syncManager == null) return null;
-        return syncManager.mAccountObserver.getAccountKeyWhere();
+        if (syncManager != null && syncManager.mAccountObserver != null) {
+            return syncManager.mAccountObserver.getAccountKeyWhere();
+        }
+        return null;
     }
 
     public class SyncStatus {