Add method to IFoo for testing NULL interfaces.

Bug: 32410513
Test: mma, hidl_test
Change-Id: I791c3a95e670a859e5e494ead987d2a93f5047a5
diff --git a/tests/bar/1.0/default/Bar.h b/tests/bar/1.0/default/Bar.h
index 6fea563..ec55e8b 100644
--- a/tests/bar/1.0/default/Bar.h
+++ b/tests/bar/1.0/default/Bar.h
@@ -60,6 +60,8 @@
             const hidl_vec<sp<android::hardware::IBinder> > &in,
             haveAVectorOfGenericInterfaces_cb _hidl_cb) override;
 
+    Return<void> echoNullInterface(const sp<IFooCallback> &cb, echoNullInterface_cb _hidl_cb) override;
+
     // Methods from ::android::hardware::tests::bar::V1_0::IBar follow.
     Return<void> thisIsNew()  override;