Only invalidate cache on del style when caching is enabled

lib/cartodb/cartodb_windshaft.js

@@ -73,7 +73,7 @@ var CartodbWindshaft = function(serverOptions) {
         ws.doCORS(res);
         Step(
             function(){
-                serverOptions.flushCache(req, Cache, this);
+                serverOptions.flushCache(req, serverOptions.cache_enabled ? Cache : null, this);
             },
             function(err, data){
                 if (err){

lib/cartodb/server_options.js

@@ -155,7 +155,9 @@ module.exports = function(){
             },
             function(err, data){
                 if (err) throw err;
-                Cache.invalidate_db(req.params.dbname, req.params.table);
+                if(Cache) {
+                  Cache.invalidate_db(req.params.dbname, req.params.table);
+                }
                 callback(null, true);
             }
         );