Avoid flaky test fail due to no Subscription service.

Fix: 340875634
Test: atest passed
Change-Id: Id922ace830f25dd730cad2d8aa19177988b6670d

src/com/android/settings/network/SubscriptionUtil.java

@@ -643,8 +643,13 @@ public class SubscriptionUtil {
 
         final SubscriptionManager subscriptionManager = context.getSystemService(
                 SubscriptionManager.class);
-        String rawPhoneNumber = subscriptionManager.getPhoneNumber(
+        String rawPhoneNumber = "";
+        try {
+            rawPhoneNumber = subscriptionManager.getPhoneNumber(
                     subscriptionInfo.getSubscriptionId());
+        } catch (IllegalStateException e) {
+            Log.e(TAG, "Subscription service unavailable : " + e);
+        }
         if (TextUtils.isEmpty(rawPhoneNumber)) {
             return null;
         }