Store intermediate resources in reducer so the array is not empty the first run. Addresses #1590

middleman-core/lib/middleman-core/sitemap/store.rb

@@ -211,22 +211,23 @@ module Middleman
 
           @app.logger.debug '== Rebuilding resource list'
 
-          @resources = @resource_list_manipulators.reduce([]) do |result, (_, inst)|
-            newres = inst.manipulate_resource_list(result)
+          @resources = []
+
+          @resource_list_manipulators.each do |(_, inst)|
+            @resources = inst.manipulate_resource_list(@resources)
 
             # Reset lookup cache
             reset_lookup_cache!
-            newres.each do |resource|
+            
+            @resources.each do |resource|
               @_lookup_by_path[resource.path] = resource
               @_lookup_by_destination_path[resource.destination_path] = resource
             end
 
-            newres
-          end
-
             invalidate_resources_not_ignored_cache!
           end
         end
+      end
 
       private