- vector<Item*> cols (root->broken_col_range (sp->get_bound (LEFT)->get_column (),
- sp->get_bound (RIGHT)->get_column ()));
+ Drul_array<Item*> bounds (sp->get_bound (LEFT),
+ sp->get_bound (RIGHT));
+ if (!bounds[LEFT] || !bounds[RIGHT])
+ return SCM_UNSPECIFIED;
+
+ vector<Item*> cols (root->broken_col_range (bounds[LEFT]->get_column (),
+ bounds[RIGHT]->get_column ()));