fix: responds with http status 422

Author: gildesmarais

app.rb

@@ -90,10 +90,16 @@ def self.development? = ENV['RACK_ENV'] == 'development'
           config = Html2rss::Configs.find_by_name(name)
 
           if (params = request.params).any?
+            config = config.dup
             config[:params] ||= {}
             config[:params].merge!(params)
           end
 
+          unless config[:strategy]
+            config = config.dup if config.frozen?
+            config[:strategy] ||= Html2rss::RequestService.default_strategy_name
+          end
+
           feed = Html2rss.feed(config)
 
           HttpCache.expires(response, feed.channel.ttl.to_i * 60, cache_control: 'public')
@@ -107,10 +113,16 @@ def self.development? = ENV['RACK_ENV'] == 'development'
           config = LocalConfig.find(File.basename(config_name_with_ext, '.*'))
 
           if (params = request.params).any?
+            config = config.dup
             config[:params] ||= {}
             config[:params].merge!(params)
           end
 
+          unless config[:strategy]
+            config = config.dup if config.frozen?
+            config[:strategy] ||= Html2rss::RequestService.default_strategy_name
+          end
+
           feed = Html2rss.feed(config)
 
           HttpCache.expires(response, feed.channel.ttl.to_i * 60, cache_control: 'public')