Deleting References to Resolve Regeneration Failures
When regeneration fails due to a missing reference, you can investigate and resolve the failure by deleting the missing reference. Open the Reference Viewer dialog box to resolve the failure. Select the component with a failed reference, right-click and select 
Information > 
Reference Viewer to open the Reference Viewer
Information > Reference Viewer to open the Reference Viewer | The Delete Reference command is unavailable for references that affect feature structure or a logical collection. |