It is only warning, but not an error. I will review this warnig on my test site. You can disable warnings in Joomla general settings (tab "System", parameter "Error messages" - "By default")
New version of IPrice minimart 2.4.2 for Joomla 4.x.
What`s new:
Added "Do not use cart" option. In this mode, you can select the necessary products on the page and immediately submit the order by filling out the contact information. The shopping cart is not used in this case. This mode is suitable for organizing a quick order of a small number of goods or for costing and ordering services. Demo price list without using a shopping cart. Demo of a catalog without using a shopping cart.