After creating a new block with a locationlist attribute in page builder (eg. Landing Page), reference to another content in that block is not removed from the ezpage_attributes table, when the content itself is removed.

Steps to reproduce:
1. Define a block for the page builder with a locationlist attribute
2. Create a new Landing Page named "Page1"
3. Create second Landing Page named "Main Page"
4. On "Main page" add a new block with a locationlist attribute
5. Click "Select content" and select "Page1"
6. Publish "Main Page" (after that in DB "ezpage_attributes" table new entry with "Page1" LocationId appear)
7. Delete "Page1" (Send to trash)

Result:
Reference entry stays in the DB "ezpage_attributes" table and when trying to edit block with locationlist attribute, 404 error appears.

Expected:
Reference entry should be removed from "ezpage_attributes" table.
(after manual delete of this entry, the block locationlist attribute can be edited)