It's not possible to edit a Content Type with ezobjectrelation field type that has a deleted starting location defined.

Steps to reproduce:
1. Login as admin
2. Go to Admin -> Content Types
3. Open "Content" group
4. Start creating a new Content Type. Enter:

• Name: TestCt
• Identifier: testct

5. Add field type: "Content relations (multiple)
6. Select starting location for that field type: Media/Multimedia
7. Save
8. Navigate to "Media/Multimedia" Content
9. Send it to Trash
10. Go to Admin -> Content Types -> Content -> TestCt
11. Click on the pencil to edit

Result:
Symfony error:

An exception has been thrown during the rendering of a template ("Could not find 'location' with identifier '52'") in "@admin/admin/content_type/field_types.html.twig".