* Fixed bug where PayPal Express was adding tax twice for subscription charges. (This does not fix existing subscriptions on the PayPal side.)
* Fixed bug with the Stripe Webhook where non-PMPro orders were being added to PMPro via the webhook. If the customer_id cannot be found (i.e. it's a non-PMPro customer), the order is ignored. (Thanks, Jacob Glenn)
* The getMemberOrderByPaymentTransactionID() function has been updated to return false if no payment_transaction_id is passed in (instead of finding the first order where the id is blank). This is inline with the getMemberOrderBySubscriptionTransactionID() function.
Fixed bug where user_id = '' was breaking on some MySQL setups and keeping the pmpro_membership_orders table from being populated.