Paypal IPN orders not recorded if order-total addons are missing language files

In 1.3.8 in includes/classes/order_total.php, additional messaging was added to warn if an order total module's language file could not be included. This is new to 1.3.8 and did not exist in 1.3.7.

However, it uses the $messageStack object, which doesn't seem to be there when a paypal IPN transaction is run. Possible solutions to this are to create a $messageStack in ipn_main_handler.php (prob. safest) or to check is_object($messageStack) in the includes/classes/order_total.php. I have verified for certain that on installations where this message is issued, orders are not entered into the database, and commenting out the call to add or add_session is a successful workaround.

So ... you're saying that an improperly-installed addon order-total module would be the case when this bug would cause a failure?

And, as such, the bug would not be triggered if the addon order-total module is correctly-written and correctly-installed?

Yes - the situation occurs as a result of an incomplete install. For instance, someone adds a new language to their cart, but does not install the order total language includes for that language. Or someone just deletes an order total language file.