Error at changing layout when creating New Category

Image 1 is the original image when creating New Category.
Image 2 is when I change the layout, and it's keeping loading without reply.
Image 3 is the result when I checked the console, it said that that link got 500 error.
Image 4 is when I linked to that link, and it showed " Call to a member function get() on null ".

The link is:
/administrator/index.php?option=com_flexicontent&task=templates.getlayoutparams&ext_view=category&ext_option=com_flexicontent&ext_name=blog&ext_id=0&layout_name=category&ext_type=templates&directory=blog&format=raw&c608c93f6bf8cf73acf37f4b0544c4a3=1

But this DIDN'T happen when I updated existed category. So I checked if there is any different between creating and updating category.

When creating new, the "ext_id" in the link is 0. When updating existed category, the "ext_id" looks like the id of the template. So it looks like this issue happens when ext_id=0, because when I change the ext_id manually in the link, it works, shows the reply. (Check image 5).

My flexicontent version is up to date, 3.3.1.6. It still happened when I downgrade to 3.3.1.5. I have another website working with 3.2, and it works well. I can't confirm if it happened after I upgraded to 3.3, because I haven't created new category for a long time.

Is this a bug, or this is the issue of nginx/php setting? I can't find the solution to solve this issue by changing nginx/php setting.

Thanks,
Lomu

maybe you have an old or custom template with a bad xml ?

Hi Micker
Yes I have some old templates with old version xmls.
But this happened when I chose "blog", and this template and xml should be updated when upgrading flexicontent, right?
Or I have to update the xml of all old templates?
I will check it.
Thanks,
Lomu

Hi micker
I'm thinking that if it's caused by bad xml, this should happen when editing category, right?
But this only happened when creating a new one. It works well when editing.
Any idea?
Thanks,
Lomu

1 try to rmove all old template
2 clean your site cache and expired cache
3 redo your test
i think all xml are loaded when you change