Problems with Stock quantity to 0

Hello,

I have a issue with tis plugin when I want to change total of quantity of stock in a variation or simple product.
If I change the value 1 to 0 or 4 to 0 don’t save the new value, it′s impossible to put the stock with 0 value. I must go to edit directly the product, and change its each variationn or simple product stock and put the quantity of stock to 0.

Then when i became to WooCommerce Stock Manager the values are changed.

I tried with:

Wordppress versión 4.8.3
WooCommerce Stock Manager Versión 1.2.0

and with 2 last versions of woomcommerce 3.2.2 & 3.2.3

I love this plugin, but with this issue is very difficult to work because everyday many products will have 0 value after the day.

Sorry for me english and best regards.