Error message when checkout

Error message when checkout

After all address details have been entered (checkout step 2), the next error message will be displayed in the frontend when clicking next:
array_diff(): Argument #1 ($array) must be of type array, null given

This message will also displayed when i go in the backend to Joomshopping > Clients > Username and click on save.

Today I updated Joomshopping from version 5.3.0 to 5.3.1.
I don't know if this caused the problem, but yesterday I didn't have this problem.

The website is still under construction and not yet vissable for public. It is therefore not possible to post a link publicly here.

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Aw: Error message when checkout

Problem solved.
Another third party plugin was not up to date :-)