[18.0] stock_picking_tier_validation: Error on Batch Transfer

[nurinayati]

Module

stock_picking_tier_validation

Describe the bug

Error when validating a batch transfer - ValueError: Expected singleton: stock.picking(29, 30)

To Reproduce

Affected versions: 18.0

Steps to reproduce the behavior:

1. Create a batch transfer and stock picking tier validation set up
2. Validate the batch transfer

Expected behavior
It should show the warning message that the stock picking is under review and needs to be approved