Assignee None does not work while Language is Chinese Taiwan

Description of the problem

Steps works:

1. Assignee: None
   https://gitlab.com/tortoisegit/tortoisegit/issues?scope=all&utf8=%E2%9C%93&state=opened
   
   
   
2. Press Enter

It works (The "None X" stays there.)
https://gitlab.com/tortoisegit/tortoisegit/issues?scope=all&utf8=%E2%9C%93&state=opened&assignee_id=None

Steps does not work:

1. Change Language to Chinese Taiwan
   
2. Go back the issue list (https://gitlab.com/tortoisegit/tortoisegit/issues?scope=all&utf8=%E2%9C%93&state=opened&assignee_id=None)
3. Press F5 & it's good for now
   
4. Clear up by pressing X
   
5. Assignee: None again
   
   
6. Press Enter & GitLab shows up some user I don't know
   (https://gitlab.com/tortoisegit/tortoisegit/issues?scope=all&utf8=%E2%9C%93&state=opened&assignee_username[]=None)
   

Possible key point: assignee_id vs. assignee_username

So, I can see the URL is different:

https://gitlab.com/tortoisegit/tortoisegit/issues?scope=all&utf8=%E2%9C%93&state=opened&assignee_id=None

vs.

https://gitlab.com/tortoisegit/tortoisegit/issues?scope=all&utf8=%E2%9C%93&state=opened&assignee_username[]=None

Which Group/Project (with full path) is experiencing the issue?

https://gitlab.com/tortoisegit/tortoisegit/issues?scope=all&utf8=%E2%9C%93&state=opened&assignee_username[]=None

Approximate date/time when the error occurred.

Today: 2019-11-29

Describe what you were doing right before the issue occurred.

It is my first time to hit this issue. Because the Language is English usually.