Unable to add multiple items to armoury

[Yeldur]

Describe the bug
In v100 (d04661a) we added the following:
"You can now own several copy of an items to dress your whole clan + QOL improvement "

This currently is not possible, as it errors when you attempt to purchase another item, thus preventing it from being purchased a second time.

To Reproduce

1. Buy item
2. Add to armoury
3. Attempt to purchase another item
   OR
4. Buy item
5. Buy second item

Expected behavior
Should allow for multiple purchases of single item

Screenshots/Videos
N/A (generic error splash screen)

Context

• Browser (in case of a bug on the website) [e.g. chrome, firefox] FireFox (does not seem to be browser related however)