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/native/libcore_util_CharsetUtils.cc b/runtime/native/libcore_util_CharsetUtils.cc
index 2590452..e51b6d2 100644
--- a/runtime/native/libcore_util_CharsetUtils.cc
+++ b/runtime/native/libcore_util_CharsetUtils.cc
@@ -155,7 +155,7 @@
   ScopedObjectAccess soa(env);
   StackHandleScope<1> hs(soa.Self());
   Handle<mirror::String> string(hs.NewHandle(soa.Decode<mirror::String>(java_string)));
-  if (string.Get() == nullptr) {
+  if (string == nullptr) {
     return nullptr;
   }
 
@@ -192,7 +192,7 @@
   ScopedObjectAccess soa(env);
   StackHandleScope<1> hs(soa.Self());
   Handle<mirror::String> string(hs.NewHandle(soa.Decode<mirror::String>(java_string)));
-  if (string.Get() == nullptr) {
+  if (string == nullptr) {
     return nullptr;
   }