Error when saving product with more than one variant with same sku

[oadslug]

Description

Received an error when attempting to save a product with more than one variant with the same sku (as opposed to just a 'Couldn't save product' CMS warning).

SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry '99111' for key 'craft_commerce_variants_sku_unq_idx'
The SQL being executed was: INSERT INTO `craft_commerce_variants` (`id`, `productId`, `sku`, `price`, `width`, `height`, `length`, `weight`, `minQty`, `maxQty`, `stock`, `isDefault`, `sortOrder`, `hasUnlimitedStock`, `dateCreated`, `uid`, `dateUpdated`) VALUES (1390, 1388, '99111', '25', '0', '0', '0', '0', NULL, NULL, 0, 0, 2, 1, '2018-06-26 04:00:30', '0e79b813-a08a-497e-8f82-fd9e242be007', '2018-06-26 04:00:30')

Additional info

• Craft version: Craft CMS 3.0.12
• PHP version: 7.0.13
• Database driver & version: MySQL 5.6.34
• Plugins & versions: Commerce 2.0.0-beta.5

[lukeholder]

Thanks fixed for the next release.