Don't crash if an invalid always-on VPN profile is configured.

This is currently being hit because Settings does not clear the
always-on VPN configuration when the corresponding VPN profile is
deleted. This will be fixed in Settings, but there's no harm in
being robust to invalid configurations here.

Bug: 23625458
Change-Id: Id185a54d5892339197cd40026df5174debd957cf

services/core/java/com/android/server/ConnectivityService.java

@@ -3212,6 +3212,11 @@ public class ConnectivityService extends IConnectivityManager.Stub
             final String profileName = new String(mKeyStore.get(Credentials.LOCKDOWN_VPN));
             final VpnProfile profile = VpnProfile.decode(
                     profileName, mKeyStore.get(Credentials.VPN + profileName));
+            if (profile == null) {
+                Slog.e(TAG, "Lockdown VPN configured invalid profile " + profileName);
+                setLockdownTracker(null);
+                return true;
+            }
             int user = UserHandle.getUserId(Binder.getCallingUid());
             synchronized(mVpns) {
                 setLockdownTracker(new LockdownVpnTracker(mContext, mNetd, this, mVpns.get(user),