[BuG] Storage location not preserved on error in new purchases

[cielf]

Summary

On a new purchase, if you select a storage location, but have an error, the storage location resets to the first one in the list. Fix it so it remains.

Why?

If this is not noticed, the purchase will go to the wrong storage location, and the inventory will not be what is expected. This is bad.

Details

Recreation

Purchases | New Purchase
Fill in partial information -- I added the vendor, selected a storage location that was not the first one, left the prices empty, and added one item. Hit save.
You will see that the storage location is back to the first one ('Bulk Storage Location').

Criteria for completion

• Storage location is preserved on error
• tests to demonstrate this behaviour

[aniketpatidar]

@cielf I would like to contribute to this one!