AssertionError: AbstractLinkable._notifier is None in _notify_links method

[Stefal]

Describe the bug
When starting the new web server (gunicorn) i get these errors messages:

Traceback (most recent call last):
  File "src/gevent/_abstract_linkable.py", line 287, in gevent._gevent_c_abstract_linkable.AbstractLinkable._notify_links
  File "src/gevent/_abstract_linkable.py", line 333, in gevent._gevent_c_abstract_linkable.AbstractLinkable._notify_links
AssertionError: (None, <callback at 0x7f755601ac80 args=([],)>)
2024-06-11T19:50:43Z <callback at 0x7f755601ac80 args=([],)> failed with AssertionError

To Reproduce
Steps to reproduce the behavior:

1. Start the web server, or read the logs

Expected behavior
No error messages

Software/Hardware (please complete the following information):

• RTKBase release number 2.6
• gevent 24.2.1
• gunicorn 22.0.0

Additional context

The server runs correctly. We can ignore this message.
Seems related to gevent/gevent#1895 but I don't use a debug tool.