Fix EZP-23620: Segmentation fault error when copying subtree

The ezobjectrelationlist attribute copies related objects that are in the subtree of it's own object, and objects that have no node. The latter also includes objects in trash, leading to an infinite loop in certain cases. Changed to never copy objects that are in trash.
Merge pull request #1113 from glye/ezp-23620_segfault_copy_subtree

Fix EZP-23620: Segmentation fault error when copying subtree