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/compiler/optimizing/code_generator.cc b/compiler/optimizing/code_generator.cc
index d68aa51..bac16cd 100644
--- a/compiler/optimizing/code_generator.cc
+++ b/compiler/optimizing/code_generator.cc
@@ -1419,7 +1419,7 @@
 
 QuickEntrypointEnum CodeGenerator::GetArrayAllocationEntrypoint(Handle<mirror::Class> array_klass) {
   ScopedObjectAccess soa(Thread::Current());
-  if (array_klass.Get() == nullptr) {
+  if (array_klass == nullptr) {
     // This can only happen for non-primitive arrays, as primitive arrays can always
     // be resolved.
     return kQuickAllocArrayResolved32;