[Settings] Should back to previous page when removing the SIM (subinfo is null)

Test: atest
Bug: 211843783
Change-Id: I5fc2ecdf26848af246baab42a11c239a7aa82ee1

src/com/android/settings/network/telephony/MobileNetworkSettings.java

@@ -280,6 +280,11 @@ public class MobileNetworkSettings extends AbstractMobileNetworkSettings {
             return;
         }
 
+        if (SubscriptionUtil.getSubscriptionOrDefault(getContext(), mSubId) == null) {
+            finishFragment();
+            return;
+        }
+
         ThreadUtils.postOnMainThread(() -> {
             mActiveSubscriptionsListenerCount = 0;
             redrawPreferenceControllers();