check if reveal theme exists

lib/response.js

@@ -13,6 +13,7 @@ var moment = require('moment')
 var config = require('./config')
 var logger = require('./logger')
 var models = require('./models')
+var utils = require('./utils')
 
 // public
 var response = {
@@ -574,7 +575,7 @@ function showPublishSlide (req, res, next) {
         updatetime: updatetime,
         url: origin,
         body: markdown,
-        theme: meta.slideOptions.theme,
+        theme: utils.isRevealTheme(meta.slideOptions.theme),
         meta: JSON.stringify(extracted.meta),
         useCDN: config.usecdn,
         owner: note.owner ? note.owner.id : null,