Fix mobile data settings UI bug.

Change-Id: Id13cf0e88c176cd42b051f444f4b69382625df66
Bug: 64465388
Test: manual
diff --git a/src/com/android/phone/MobileDataPreference.java b/src/com/android/phone/MobileDataPreference.java
index e1d0528..fe70028 100644
--- a/src/com/android/phone/MobileDataPreference.java
+++ b/src/com/android/phone/MobileDataPreference.java
@@ -114,6 +114,9 @@
 
     @Override
     public void performClick(PreferenceScreen preferenceScreen) {
+        if (!isEnabled() || !SubscriptionManager.isValidSubscriptionId(mSubId)) {
+            return;
+        }
         final SubscriptionInfo currentSir = mSubscriptionManager.getActiveSubscriptionInfo(
                 mSubId);
         final SubscriptionInfo nextSir = mSubscriptionManager.getDefaultDataSubscriptionInfo();