The cart link can increase the quantity but can not decrease it

Thank you Soft79 for this awesome piece of code.

Issue: The cart link can increase the quantity but can not decrease it.

Example:

http://www.example.com?fill_cart=3×44

This URL will populate the cart with 2x item with id 44.

http://www.example.com?fill_cart=5×44

This URL will increase the quantity to 5x from 2x

But URL

http://www.example.com?fill_cart=1×44

doesn’t reduce the quantity to 1x from 5x.

Hope this can be addressed.
Thanks, Manju

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