Replace NULL with nullptr

Also fixed some lines that were too long, and a few other minor
details.

Change-Id: I6efba5fb6e03eb5d0a300fddb2a75bf8e2f175cb
diff --git a/runtime/interpreter/unstarted_runtime.cc b/runtime/interpreter/unstarted_runtime.cc
index 61def35..f30c93a 100644
--- a/runtime/interpreter/unstarted_runtime.cc
+++ b/runtime/interpreter/unstarted_runtime.cc
@@ -915,7 +915,7 @@
   Runtime* runtime = Runtime::Current();
   ClassLinker* class_linker = runtime->GetClassLinker();
   mirror::Class* array_class = class_linker->FindArrayClass(self, &element_class);
-  if (UNLIKELY(array_class == NULL)) {
+  if (UNLIKELY(array_class == nullptr)) {
     CHECK(self->IsExceptionPending());
     return;
   }