Fix null pointer in SubscriptionUtil

Sometimes we get null sub info which causes a crash. This just
makes it so that if we see that we treat it as inactive since
there isn't really a world where an active null sub info makes
sense.

Test: atest SubscriptionUtilTest
Bug: 131603073
Change-Id: Id5ecbecf011e19ff02d9465e0571b1d17c83de9a

tests/robotests/src/com/android/settings/network/SubscriptionUtilTest.java

@@ -187,4 +187,9 @@ public class SubscriptionUtilTest {
         assertThat(subs).isNotNull();
         assertThat(subs).hasSize(2);
     }
+
+    @Test
+    public void isInactiveInsertedPSim_nullSubInfo_doesNotCrash() {
+        assertThat(SubscriptionUtil.isInactiveInsertedPSim(null)).isFalse();
+    }
 }