entc/gen: add eager-load edges to query clone (#888)

Closed #878

examples/privacyadmin/ent/user_query.go

@@ -222,6 +222,9 @@ func (uq *UserQuery) ExistX(ctx context.Context) bool {
 // Clone returns a duplicate of the query builder, including all associated steps. It can be
 // used to prepare common query builders and use them differently after the clone is made.
 func (uq *UserQuery) Clone() *UserQuery {
+	if uq == nil {
+		return nil
+	}
 	return &UserQuery{
 		config:     uq.config,
 		limit:      uq.limit,