Пишу APi, вылетает ошибка при запросе. В чем дело?

Запрос curl http://localhost:5000/recStructs -d "currency=BTC&maturity=25JUN&amount=1&fut_hedge_flag=True" -X GET -v

 PARS BTC 25JUN 1 True
    [2021-05-08 23:40:39,576] ERROR in app: Exception on /recStructs [GET]
    Traceback (most recent call last):
      File "C:\Users\Vladik\AppData\Local\Programs\Python\Python39\lib\site-packages\flask\app.py", line 1950, in full_dispatch_request
        rv = self.dispatch_request()
      File "C:\Users\Vladik\AppData\Local\Programs\Python\Python39\lib\site-packages\flask\app.py", line 1936, in dispatch_request
        return self.view_functions[rule.endpoint](**req.view_args)
      File "C:\Users\Vladik\AppData\Local\Programs\Python\Python39\lib\site-packages\flask_restful\__init__.py", line 468, in wrapper
        resp = resource(*args, **kwargs)
      File "C:\Users\Vladik\AppData\Local\Programs\Python\Python39\lib\site-packages\flask\views.py", line 
    89, in view
        return self.dispatch_request(*args, **kwargs)
      File "C:\Users\Vladik\AppData\Local\Programs\Python\Python39\lib\site-packages\flask_restful\__init__.py", line 583, in dispatch_request
        resp = meth(*args, **kwargs)
      File "C:\Users\Vladik\Desktop\calculator_api\main.py", line 50, in get
        rec_data = utils.generate_rec_structures(currency, maturity)
      File "C:\Users\Vladik\Desktop\calculator_api\utils.py", line 397, in generate_rec_structures
        strike_0_str = str(int(strike_0))
    TypeError: int() argument must be a string, a bytes-like object or a number, not 'NoneType'
    127.0.0.1 - - [08/May/2021 23:40:39] "←[35m←[1mGET /recStructs HTTP/1.1←[0m" 500 -