Fix import to objects

[npracht]

Q	A
Bug fix? (use the a.b branch)	✅
New feature/enhancement? (use the a.x branch)
Deprecations?
BC breaks? (use the c.x branch)
Automated tests included?
Related user documentation PR URL	not relevant
Related developer documentation PR URL	not relevant
Issue(s) addressed

Description:

If you import items of a custom objects, you have error in UI if you have a mandatory field in the object even if mapped:

Steps to test this PR:

1. Setup a custom object
2. Set 1 custom object field as mandatory
3. Do an import AND map your mandatory field
4. See error thrown even if mapped.