Prevent NoMethodError in generating an error message

lib/lrama/grammar.rb

@@ -166,7 +166,7 @@ def translated_printer_code(tag)
         when ref.type == :at # @n
           raise "@#{ref.number} can not be used in %printer."
         else
-          raise "Unexpected. #{code}, #{ref}"
+          raise "Unexpected. #{self}, #{ref}"
         end
 
         t_code[first_column..last_column] = str
@@ -205,7 +205,7 @@ def translated_user_code
           i = -ref.position_in_rhs + ref.number
           str = "(yylsp[#{i}])"
         else
-          raise "Unexpected. #{code}, #{ref}"
+          raise "Unexpected. #{self}, #{ref}"
         end
 
         t_code[first_column..last_column] = str
@@ -235,7 +235,7 @@ def translated_initial_action_code
         when ref.type == :at # @n
           raise "@#{ref.number} can not be used in initial_action."
         else
-          raise "Unexpected. #{code}, #{ref}"
+          raise "Unexpected. #{self}, #{ref}"
         end
 
         t_code[first_column..last_column] = str

lib/lrama/states.rb

@@ -198,7 +198,7 @@ def transition(sym)
     def find_reduce_by_item!(item)
       reduces.find do |r|
         r.item == item
-      end || (raise "reduce is not found. #{item}, #{state}")
+      end || (raise "reduce is not found. #{item}")
     end
 
     def default_reduction_rule=(default_reduction_rule)