Fix collection post 500 when not logged in

This reverts some code from 5429ca4a, which broke collection post
loading on blog posts when not logged in.

posts.go

@@ -1390,7 +1390,7 @@ Are you sure it was ever here?`,
 			return err
 		}
 	}
-	p.IsOwner = owner != nil && p.OwnerID.Valid && u.ID == p.OwnerID.Int64
+	p.IsOwner = owner != nil && p.OwnerID.Valid && owner.ID == p.OwnerID.Int64
 	p.Collection = coll
 	p.IsTopLevel = app.cfg.App.SingleUser