Fix invalid values in RelationListFieldSerializer.

[Faakhir30]

Closes #1745

Filtered NoneType items from the resulting list at RelationListFieldSerializer.

I guess we don't need to update this also in RelationChoiceFieldSerializer, as it is returning a single RelationValue or None value, so it should be fine this way.

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📚 Documentation preview 📚: https://plonerestapi--1818.org.readthedocs.build/

[mister-roboto]

@Faakhir30 thanks for creating this Pull Request and helping to improve Plone!

TL;DR: Finish pushing changes, pass all other checks, then paste a comment:

@jenkins-plone-org please run jobs

To ensure that these changes do not break other parts of Plone, the Plone test suite matrix needs to pass, but it takes 30-60 min. Other CI checks are usually much faster and the Plone Jenkins resources are limited, so when done pushing changes and all other checks pass either start all Jenkins PR jobs yourself, or simply add the comment above in this PR to start all the jobs automatically.

Happy hacking!

[wesleybl]

I think it would be interesting to do a test for this here:

plone.restapi/src/plone/restapi/tests/test_dxcontent_serializer.py

Line 60 in 7b1f0f4

class TestDXContentSerializer(unittest.TestCase):

You can use the test_relationlist_field field:

plone.restapi/src/plone/restapi/tests/dxtypes.py

Line 248 in 31a18e1

test_relationlist_field = RelationList(

[Faakhir30]

@jenkins-plone-org please run jobs

[Faakhir30]

@jenkins-plone-org please run jobs

[wesleybl]

LGTM

[Faakhir30]

@jenkins-plone-org please run jobs

[davisagli]

@jenkins-plone-org please run jobs

[davisagli]

LGTM. We can merge it once the builds are green.