lib/ngt/optimizer.rb in ngt-0.2.4 vs lib/ngt/optimizer.rb in ngt-0.3.0

@@ -31,9 +31,14 @@
     end
 
     private
 
     def path(obj)
-      obj.is_a?(Ngt::Index) ? obj.path : obj
+      if obj.is_a?(Ngt::Index)
+        raise ArgumentError, "Index not saved" unless obj.path
+        obj.path
+      else
+        obj
+      end
     end
   end
 end