Add additional check in feature counter

lib/discourse_plugin_statistics/plugin.rb

@@ -56,7 +56,7 @@ module DiscoursePluginStatistics
       }
 
       increment_feature_count = lambda do |type, key, value|
-        if key == 'type'
+        if key == 'type' && !subscription_features[type.to_sym][:type][value.to_sym].nil?
           subscription_features[type.to_sym][:type][value.to_sym] += 1
         elsif !subscription_features[type.to_sym][key.to_sym].nil?
           subscription_features[type.to_sym][key.to_sym] += 1