`[object Object]` bug in Stock Entry

[agritheory]

Steps to reproduce:

• Create a Stock Entry / Material Receipt (I used the Flour item, but it should matter) and submit
• Copy the Handling Unit from that Stock Entry
• Start a new Stock Entry / Material Transfer and scan the handling unit from the previous transaction

I was not able to reproduce this error by starting with a Purchase Receipt, the Stock Entry / Material Receipt source of data in get_handling_unit seems to be part of the problem.