low_stock_amount is string

[jmatah]

Issue summary

When I fetch a WooCommerce product using this API, the variable low_stock_amount is an empty string, I believe should be an integer '0'.

Expected behavior

Always return an integer. or a 0

Actual behavior

It returns an empty string.

Steps to reproduce the problem

1. response = wcapi.get('products', params={'sku':sku}).json()
2. print(response)

##Related bug
I believe this is a related bug

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