ART: Add operator == and != with nullptr to Handle

Get it in line with ObjPtr and prettify our code.

Test: m
Change-Id: I1322e2a9bc7a85d7f2441034a19bf4d807b81a0e
diff --git a/runtime/mirror/class_ext.cc b/runtime/mirror/class_ext.cc
index efd949e..7270079 100644
--- a/runtime/mirror/class_ext.cc
+++ b/runtime/mirror/class_ext.cc
@@ -58,8 +58,8 @@
   Handle<ObjectArray<DexCache>> old_dex_caches(hs.NewHandle(h_this->GetObsoleteDexCaches()));
   ClassLinker* cl = Runtime::Current()->GetClassLinker();
   size_t new_len;
-  if (old_methods.Get() == nullptr) {
-    CHECK(old_dex_caches.Get() == nullptr);
+  if (old_methods == nullptr) {
+    CHECK(old_dex_caches == nullptr);
     new_len = increase;
   } else {
     CHECK_EQ(old_methods->GetLength(), old_dex_caches->GetLength());