Attribute error

can somebody help with this please, am building an ecommerce web and when i want to view my cart i get this error

AttributeError: 'NoneType' object has no attribute 'price'

here is my models.py

class OrderItem(models.Model):

    product = models.ForeignKey(Product, on_delete=models.SET_NULL, null=True)
    order = models.ForeignKey(Order, on_delete=models.SET_NULL, null=True)
    quantity = models.IntegerField(default=0, null=True, blank=True)
    date_added = models.DateTimeField(auto_now_add=True)

    @property
    def get_total(self):
        total = self.product.price * self.quantity
        return total

AttributeError at /cart/

'NoneType' object has no attribute 'price'

Request Method:	GET
Request URL:	http://127.0.0.1:8000/cart/
Django Version:	3.2
Exception Type:	AttributeError
Exception Value:	'NoneType' object has no attribute 'price'
Exception Location:	C:\Users\Admin\PycharmProject\MyProject\Ecommerce\shop\models.py, line 71, in get_total
Python Executable:	C:\Users\Admin\PycharmProject\MyProject\venv\Scripts\python.exe
Python Version:	3.8.2
Python Path:	['C:\\Users\\Admin\\PycharmProject\\MyProject\\Ecommerce', 'C:\\Users\\Admin\\AppData\\Local\\Programs\\Python\\Python38\\python38.zip', 'C:\\Users\\Admin\\AppData\\Local\\Programs\\Python\\Python38\\DLLs', 'C:\\Users\\Admin\\AppData\\Local\\Programs\\Python\\Python38\\lib', 'C:\\Users\\Admin\\AppData\\Local\\Programs\\Python\\Python38', 'C:\\Users\\Admin\\PycharmProject\\MyProject\\venv', 'C:\\Users\\Admin\\PycharmProject\\MyProject\\venv\\lib\\site-packages']
Server time:	Wed, 12 May 2021 08:44:09 +0000

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