Make FieldType::None() non-nullptr value to avoid undefined behaviour

test/cctest/test-field-type-tracking.cc

Index: test/cctest/test-field-type-tracking.cc
diff --git a/test/cctest/test-field-type-tracking.cc b/test/cctest/test-field-type-tracking.cc
index 9f2a6848ccfc362a961486007de9bc6638a03e3d..ae63feaedb9689d003d8e4c4ce7a41a599296ca1 100644
--- a/test/cctest/test-field-type-tracking.cc
+++ b/test/cctest/test-field-type-tracking.cc
@@ -17,6 +17,7 @@
 #include "src/global-handles.h"
 #include "src/ic/stub-cache.h"
 #include "src/macro-assembler.h"
+#include "src/types.h"
 
 using namespace v8::internal;
 
@@ -2410,6 +2411,16 @@ TEST(TransitionAccessorConstantToSameAccessorConstant) {
   TestTransitionTo(transition_op, transition_op, checker);
 }
 
+TEST(FieldTypeConvertSimple) {
+  CcTest::InitializeVM();
+  v8::HandleScope scope(CcTest::isolate());
+  Isolate* isolate = CcTest::i_isolate();
+
+  Zone zone(isolate->allocator());
+
+  CHECK_EQ(FieldType::Any()->Convert(&zone), Type::NonInternal());
+  CHECK_EQ(FieldType::None()->Convert(&zone), Type::None());
+}
 
 // TODO(ishell): add this test once IS_ACCESSOR_FIELD_SUPPORTED is supported.
 // TEST(TransitionAccessorConstantToAnotherAccessorConstant)