jsauthority: JSVAL_IS_NULL (o) to o.isNull()

Signed-off-by: Ray Strode <rstrode@redhat.com>

https://bugs.freedesktop.org/show_bug.cgi?id=105865

src/polkitbackend/polkitbackendjsauthority.cpp

@@ -1238,7 +1238,7 @@ polkit_backend_js_authority_check_authorization_sync (PolkitBackendInteractiveAu
       goto out;
     }
 
-  if (JSVAL_IS_NULL (rval))
+  if (rval.isNull())
     {
       /* this fine, means there was no match, use implicit authorizations */
       good = TRUE;