Replace (most) occurrences of mojo::Array<T>() with nullptr.

mojo/public/cpp/bindings/tests/versioning_test_service.cc

Index: mojo/public/cpp/bindings/tests/versioning_test_service.cc
diff --git a/mojo/public/cpp/bindings/tests/versioning_test_service.cc b/mojo/public/cpp/bindings/tests/versioning_test_service.cc
index ba76da2d82e57b63b65af240a8ee9e19b375043a..0896b8c42b1ef4ebd6d6c44d11a855defbe20258 100644
--- a/mojo/public/cpp/bindings/tests/versioning_test_service.cc
+++ b/mojo/public/cpp/bindings/tests/versioning_test_service.cc
@@ -67,12 +67,12 @@ class HumanResourceDatabaseImpl : public HumanResourceDatabase {
                      bool retrieve_finger_print,
                      const QueryEmployeeCallback& callback) override {
     if (employees_.find(id) == employees_.end()) {
-      callback.Run(nullptr, Array<uint8_t>());
+      callback.Run(nullptr, nullptr);
       return;
     }
-    callback.Run(employees_[id]->employee.Clone(),
-                 retrieve_finger_print ? employees_[id]->finger_print.Clone()
-                                       : Array<uint8_t>());
+    callback.Run(
+        employees_[id]->employee.Clone(),
+        retrieve_finger_print ? employees_[id]->finger_print.Clone() : nullptr);
   }
 
   void AttachFingerPrint(uint64_t id,