8240529: CheckUnhandledOops breaks NULL check in Modules::define_module

Reviewed-by: coleenp, lfoltan, hseigel

src/hotspot/share/classfile/modules.cpp

@@ -453,7 +453,7 @@ void Modules::define_module(jobject module, jboolean is_open, jstring version,
 
   // If the module is defined to the boot loader and an exploded build is being
   // used, prepend <java.home>/modules/modules_name to the system boot class path.
-  if (loader == NULL && !ClassLoader::has_jrt_entry()) {
+  if (h_loader.is_null() && !ClassLoader::has_jrt_entry()) {
     ClassLoader::add_to_exploded_build_list(module_symbol, CHECK);
   }
 }