[Bug] Unable to Add Variants to an Inventory Item

[anuj-ever]

Issue:

Users are unable to add variants to an inventory item. This issue is preventing the proper management and tracking of inventory items with different variants.

Steps to Reproduce:

1. Go to the inventory screen.
2. Select an inventory item.
3. Attempt to add variants to the selected inventory item.
4. Observe that the system does not allow the addition of variants or the process fails.

Acceptance Criteria:

• Users are able to add variants to an inventory item without any issues.
• The addition of variants works correctly and is reflected in the inventory system.

[evereq]

@samuelmbabhazi can you work to fix this bug please? As it blocks testing of functionality by Anuj!