Column purchaseTotal cannot be null

[RaederDev]

Description

This error gets thrown in the CMS if the user removes the Purchase total field content.
Is there no validation of field values done in the CMS??

SQLSTATE[23000]: Integrity constraint violation: 1048 Column 'purchaseTotal' cannot be null
The SQL being executed was: UPDATE `commerce_discounts` SET `perUserLimit`=1, `perEmailLimit`=1, `totalUseLimit`=0, `purchaseTotal`=NULL, `purchaseQty`=0, `maxPurchaseQty`=0, `baseDiscount`='-16.6667', `perItemDiscount`='-0', `percentDiscount`='-0', `excludeOnSale`=0, `freeShipping`=0, `allGroups`=1, `allPurchasables`=1, `allCategories`=1, `enabled`=1, `stopProcessing`=1, `dateUpdated`='2019-01-30 18:42:00' WHERE `id`=2

Steps to reproduce

1. Create Discount
2. Delete Value in Purchase Total Field
3. Click save

Additional info

• Craft version: Craft Pro 3.1.6.1
• PHP version: 7.2.13
• Database driver & version: MySQL 5.5.5
• Craft commerce version: 2.0.2

[RaederDev]

Same also happens with a lot of other fields in the discount section for example but not limited to: maxPurchaseQty, purchaseQty, totalUseLimit, perUserLimit, perEmailLimit

[lukeholder]

Thanks fixed for the next release.