Could not save Source Item Configuration - error when assigning additional source to the Complex products

[smoskaluk]

Preconditions

1. Magento MSI
2. Bundle, Configurable and Grouped products created
3. Additional Source created

Steps to reproduce

1. Open one of these products to edit in admin
2. Click button "Assign Sources"
3. Select new Source to assign
4. Click button "Done"
5. Set Qty for this new Source
6. Click button "Save"

Expected result

1. Product has to be saved
2. New Source has to be assigned

Actual result

1. Exception message "Could not save Source Item Configuration"
2. New Source is not assigned

[naydav]

@smoskaluk
Complex product does not have Source Items (only children of complex product can have Source Items )

But need to recheck that Exception message "Could not save Source Item Configuration" is fixed in current dev branch