Fix crash when MultipathPolicyTracker cannot get IMSI

Catch the exception when cannot get IMSI to fix races that
network establish/tear down is not in-sync with SIM.
If this happens, this will be automatically recovered when
the next onCapabilitiesChanged event fires.

Test: FrameworksNetTests
Fix: 212399727
Change-Id: I3877806c0f98d8e7e3a77df75738b1799e4b68d3

services/core/java/com/android/server/connectivity/MultipathPolicyTracker.java

@@ -71,7 +71,6 @@ import java.time.ZoneId;
 import java.time.ZoneOffset;
 import java.time.ZonedDateTime;
 import java.time.temporal.ChronoUnit;
-import java.util.Objects;
 import java.util.Set;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.TimeUnit;
@@ -222,8 +221,10 @@ public class MultipathPolicyTracker {
                         "Can't get TelephonyManager for subId %d", mSubId));
             }
 
-            subscriberId = Objects.requireNonNull(tele.getSubscriberId(),
-                    "Null subscriber Id for subId " + mSubId);
+            subscriberId = tele.getSubscriberId();
+            if (subscriberId == null) {
+                throw new IllegalStateException("Null subscriber Id for subId " + mSubId);
+            }
             mNetworkTemplate = new NetworkTemplate.Builder(NetworkTemplate.MATCH_MOBILE)
                     .setSubscriberIds(Set.of(subscriberId))
                     .setMeteredness(NetworkStats.METERED_YES)