Fix NPE on devices without DPM service

Bug: 20563108
Change-Id: Ie2bda65c834ddad9db8753f7616c2754072551cd
diff --git a/service/java/com/android/server/wifi/WifiConfigStore.java b/service/java/com/android/server/wifi/WifiConfigStore.java
index 3a9131a..fd3e589 100644
--- a/service/java/com/android/server/wifi/WifiConfigStore.java
+++ b/service/java/com/android/server/wifi/WifiConfigStore.java
@@ -4174,7 +4174,7 @@
 
         final DevicePolicyManagerInternal dpmi = LocalServices.getService(
                 DevicePolicyManagerInternal.class);
-        if (dpmi.isActiveAdminWithPolicy(config.creatorUid,
+        if (dpmi != null && dpmi.isActiveAdminWithPolicy(config.creatorUid,
                 DeviceAdminInfo.USES_POLICY_DEVICE_OWNER)) {
             return uid == config.creatorUid;
         }