Add RETURN_NULL_ERROR to new apis

runtime/vm/dart_api_impl.cc

Index: runtime/vm/dart_api_impl.cc
diff --git a/runtime/vm/dart_api_impl.cc b/runtime/vm/dart_api_impl.cc
index 29f2b025f220729030a1294a916908d8515ea6eb..22c739305beae65933db4a48f90786656b2a7a3b 100644
--- a/runtime/vm/dart_api_impl.cc
+++ b/runtime/vm/dart_api_impl.cc
@@ -5888,6 +5888,9 @@ Dart_SetNativeResolver(Dart_Handle library,
 DART_EXPORT Dart_Handle
 Dart_GetNativeResolver(Dart_Handle library,
                        Dart_NativeEntryResolver* resolver) {
+  if (resolver == NULL) {
+    RETURN_NULL_ERROR(resolver);
+  }
   *resolver = NULL;
   DARTSCOPE(Thread::Current());
   const Library& lib = Api::UnwrapLibraryHandle(Z, library);
@@ -5901,6 +5904,9 @@ Dart_GetNativeResolver(Dart_Handle library,
 
 DART_EXPORT Dart_Handle Dart_GetNativeSymbol(Dart_Handle library,
                                              Dart_NativeEntrySymbol* resolver) {
+  if (resolver == NULL) {
+    RETURN_NULL_ERROR(resolver);
+  }
   *resolver = NULL;
   DARTSCOPE(Thread::Current());
   const Library& lib = Api::UnwrapLibraryHandle(Z, library);