A traceback occurs when merging two MOs when 2 step manufacturing is enabled. The issue was introduced in odoo/odoo#106411 closes odoo/odoo#120707 Taskid: 3299549 X-original-commit: 242f0f224d8941bca689e20e37c5bca3bba51afe Signed-off-by: Tiffany Chang <tic@odoo.com>