fakeservicemanager: Don't accept null binders for addService

Parity with the rest of the Service Manager APIs.

Test: atest fakeservicemanager_test
Bug: 259549842
Change-Id: I715590bc4c4f2f434ad93f82c2ba98d40334ef38
diff --git a/libs/fakeservicemanager/test_sm.cpp b/libs/fakeservicemanager/test_sm.cpp
index 71e5abe..4ddbe0c 100644
--- a/libs/fakeservicemanager/test_sm.cpp
+++ b/libs/fakeservicemanager/test_sm.cpp
@@ -50,6 +50,12 @@
         IServiceManager::DUMP_FLAG_PRIORITY_DEFAULT), OK);
 }
 
+TEST(AddService, SadNullBinder) {
+    auto sm = new ServiceManager();
+    EXPECT_EQ(sm->addService(String16("foo"), nullptr, false /*allowIsolated*/,
+        IServiceManager::DUMP_FLAG_PRIORITY_DEFAULT), android::UNEXPECTED_NULL);
+}
+
 TEST(AddService, HappyOverExistingService) {
     auto sm = new ServiceManager();
     EXPECT_EQ(sm->addService(String16("foo"), getBinder(), false /*allowIsolated*/,