grm_flow_graph.rb in rley-0.6.09

- old
+ new

@@ -137,9 +137,13 @@
           case visitee
             when Rley::GFG::StartVertex
               if first_time
                 stack.push(Branching.new(visitee, curr_edge))
                 curr_edge = stack.last.next_edge
+              elsif curr_edge.nil?
+                # Error probably caused by missing terminal symbol object
+                msg = "Undefined grammar symbol #{visitee.label.sub(/^\./, '')}"
+                raise StandardError, msg
               else
                 # Skip both start and end vertices
                 # Retrieve the corresponding return edge
                 curr_edge = get_matching_return(curr_edge)
               end