When removing the product from the shopping cart, the removing button does not work

I’m trying to make a music streaming website using Django. I have this error when i use the terminal command migrate: ValueError: Field ‘song_id’ expected a number but got ”. I don’t understand where “song_id” take a value that is not a number.
How can i fix it? this is my views.py:

i have build an other app in my django project and have a template in my templates folder and i am including the base.html from my other app