Sending Content Item to trash will produce 500 exception on Content Item that is relating to removed Content.
Step to reproduce
1. Clean installation of eZ Platform 2.5.0
2. Create a new Content Type named Content with Relations with only one field: ezobjectrelationlist.
3. Create Article - publish it.
4. Create a new Content with Relations content. As a relation add article created in step 3. Publish the new Content with Relations.
5. Go to Article created in step 3 and send it to the trash.
6. Go to Content with Relations from step 4.

Result
500 Exception

An exception has been thrown during the rendering of a template ("Notice: Trying to get property 'parentLocationId' of non-object") in "@admin/fieldtypes/preview/content_fields.html.twig".