fix: fix rstrip noneType error

[nick-kleine-tebbe]

Sometimes, HTTP_REFERER can be empty:

WrappedAttributeError at /fav/
'NoneType' object has no attribute 'rstrip'

Exception Type:	WrappedAttributeError
Exception Value:	'NoneType' object has no attribute 'rstrip'
Exception Location:	/opt/user/auth.py, line 48, in create_user
Raised during:	user.views.get_user_favorites
Python Executable:	/opt/pysetup/.venv/bin/python
Python Version:	3.13.14
Python Path:	
['/opt',
 '/opt',
 '/opt/pysetup/.venv/bin',
 '/usr/local/lib/python313.zip',
 '/usr/local/lib/python3.13',
 '/usr/local/lib/python3.13/lib-dynload',
 '/opt/pysetup/.venv/lib/python3.13/site-packages',
 'platform_back/settings/platform_back/',
 'platform_back/settings/platform_back/',
 'platform_back/settings/platform_back/',
 '/opt/pysetup/.venv/lib/python3.13/site-packages/setuptools/_vendor']
Server time:	Tue, 08 Sep 2026 06:29:11 +0000

[Amoki]

fixed by #185