broke: cannot completely delete a numeric field in grid view

[metas-lc]

Is this a bug or feature request?

bug

What is the current behavior?

this broke: #1383

Which are the steps to reproduce?

go to product price window https://w101.metasfresh.com:8443/window/540325?page=1&viewId=540325-1d7d38d43f67430b969aa3843eb54d9f
right click on a price field, pres on edit field value
use delete or backspace to remove the price
=> price is set back NOK
(this also happens in sales order, on "create purchase orders action" when you want to change a qty)

What is the expected or desired behavior?

shall be removed (see docview in price window)

[metas-lc]

IT
repeated the testcase => price was removed OK
getting some error when i'm removing it from "create purchase orders" action - but created new task, because it's not set back (the initial problem is solved) . Task: #1867