Avoid NPE in MessageOpenPgpView.updateLayout()

E/AndroidRuntime(24914): FATAL EXCEPTION: main
E/AndroidRuntime(24914): Process: com.fsck.k9, PID: 24914
E/AndroidRuntime(24914): java.lang.NullPointerException
E/AndroidRuntime(24914):    at org.openintents.openpgp.util.OpenPgpServiceConnection.<init>(OpenPgpServiceConnection.java:35)
E/AndroidRuntime(24914):    at com.fsck.k9.view.MessageOpenPgpView.updateLayout(MessageOpenPgpView.java:115)
E/AndroidRuntime(24914):    at com.fsck.k9.view.SingleMessageView.setMessage(SingleMessageView.java:623)
E/AndroidRuntime(24914):    at com.fsck.k9.fragment.MessageViewFragment$Listener$2.run(MessageViewFragment.java:602)
E/AndroidRuntime(24914):    at android.os.Handler.handleCallback(Handler.java:733)
E/AndroidRuntime(24914):    at android.os.Handler.dispatchMessage(Handler.java:95)
E/AndroidRuntime(24914):    at android.os.Looper.loop(Looper.java:136)
E/AndroidRuntime(24914):    at android.app.ActivityThread.main(ActivityThread.java:5081)
E/AndroidRuntime(24914):    at java.lang.reflect.Method.invokeNative(Native Method)
E/AndroidRuntime(24914):    at java.lang.reflect.Method.invoke(Method.java:515)
E/AndroidRuntime(24914):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:791)
E/AndroidRuntime(24914):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:607)
E/AndroidRuntime(24914):    at dalvik.system.NativeStart.main(Native Method)