If Content Types for RelationList/RelationObject field type are not specified then all should be allowed.

Steps to reproduce:
1. Create a new Content Type
2. Add "relationlist" or "relation object" field
3. Do not specify any "Allowed content types"
4. Start creating a new Content Item based on that Content Type

Expected:
All Content Types can be selected in the Relation field type

Actual:
None can be chosen.