Fix logout in some cases

src/gisaf/api/main.py

@@ -76,6 +76,7 @@ async def login_for_access_token(
 @api.get('/logout')
 async def logout(
     user: Annotated[UserRead, Depends(get_current_active_user)]):
+    if user is not None:
         logger.info(f'{user.username} ({user.id}) logged out')