ACM item type Plate cannot get an inventory unit length

We have built in an extra check for ACM items of the 'Plate' type, which means that it is no longer possible to specify 'length' as the stock unit. This was previously possible, which meant that production orders, for example, could not be financially completed. The unity check on lots checks whether an item of type 'Plate' has a lot transaction with a unit of type 'length'.