Check client null before calling and closing.

Bug: 404955994
Test: TreeHugger
Test: manual
Test: atest SafetySourceBroadcastReceiverTest
Test: atest LockScreenSafetySourceTest
Test: atest ActiveUnlockStatusUtilsTest
Test: atest WearSafetySourceTest
Flag: com.android.settings.flags.biometrics_onboarding_education
Change-Id: I34085b90fe41283e484d3b2235426676d886e69c

src/com/android/settings/biometrics/activeunlock/ActiveUnlockContentListener.java

@@ -147,6 +147,9 @@ public class ActiveUnlockContentListener {
             @NonNull String contentKey) {
         ContentResolver contentResolver = context.getContentResolver();
         ContentProviderClient client = contentResolver.acquireContentProviderClient(uri);
+        if (client == null) {
+            return null;
+        }
 
         @Nullable Bundle bundle = null;