Steps to reproduction:

• Create a content type "Test" with:
  • Field Name (ezstring)
  • Field Relations (ezcontentobjectlist)
• Create a content with this content type
  • Name: Test
  • Relations: Image from media
• Move the related image to trash
• Edit content "Test"

In the RelationList legacy converter the relation has ezcontentobject_tree_node_id = null and throw a RuntimeException:
https://github.com/ezsystems/ezpublish-kernel/blob/master/eZ/Publish/Core/Persistence/Legacy/Content/FieldValue/Converter/RelationListConverter.php#L64