WooCommerce Gravity Forms Product Add-Ons 3.6.6

* Fix: Check if the product has been loaded in the woocommerce_before_add_to_cart_form action.
* Fix: Update get_product function to prevent gravity forms from caching the result of conditional product fields.

* Fix: Call get price in edit mode so price adjustments are not filtered and hardcoded on the cart item price.

* Fix: Fix issue where fields with empty labels were not being saved to the order on WC 3.x
* Fix: Additional checks in display helper in case function called incorrectly from the theme or other extensions.
* Fix: Fix recording the gravity forms history on order placement, resolves warnings regarding undefined index.