Active entity with no supported entities.
Active entity does not have a supported entity (pipe/HVAC/cableway/and so on) associated.
Coding or data model errors in an earlier version.
Modification of the resultant support object will generate an error.
What You Should Do
Open the model.
Run the Clean Database custom command (ProgID: SP3DCleanDatabaseCmd.CCheckObj) to delete the support object in error.