items in two categories create an error when viewed (solved)

-- HikaShop version -- : 4.2.1
-- Joomla version -- : 3.9.11
-- PHP version -- : 7.1.31
-- Browser(s) name and version -- : OPERA 62.0.3331.116
-- Error-message(debug-mod must be tuned on) -- : Error: 0 - Call to a member function get() on null

I have a range of products in a normal categories which work/display well but I also have shared them with a separate 'Fathers Day' category. The carousel attached to the Fathers Day category works (i.e. slides) but any products selected from the carousel display with the following error under them;
Error: 0 - Call to a member function get() on null

I've clear all caches and product canonicals and I've set the urls to automatically generate.

I've attached a picture of the error.

Hello,

Can you give us more information about your issue by :
- Activating the Joomla debug mode ("Administration->Global configuration->System->Debug System/Language")
- Setting the "error reporting" option of the Joomla configuration to "maximum"
- Testing it again so that we can have more information about your error message through some screenshots.

We wish you a nice day!
Kind regards
Mohamed Thelji.

Thanks for the reply.
Due to time pressure I recreated the module from a copy of the original content module that cam with Hikashop. The recreated module worked so I don't know what was wrong with the old one.

I'll change this to 'solved' so that other forum member know what to do in this situation. It isn't time consuming.

Regards,
Ian and Stu