Great, no more blank pages. thanks

Another issue:

- Filters seems does not work correctly. There is only lable: Filter.
- In grid, instead of "username" is displayed only its ID

etc

edit:

it is happening in backend

I was working on this last hour.

I am not sure if it is solved for you, but I did the necessary I think.
There was an issue for interpreting the FKs from users tables because I changed lot of things there.

Anyway, the best is to recreate them because they are instancied in the old way (you cannot see it from your perspective)

So, for very old projects, I start to have some problems of interpetations the FK. If you are in this case, just recreate the concerned filters and the concerned calls of the fields.
You do not need to touch to the table fields.

I found the filter does not show up when I want to filter records by username.

Fixed. (2.5.3)

Can you try again please ?