Fix changyan undefined

Author: stevenjoezhang

scripts/filters/comment/changyan.js

@@ -8,7 +8,7 @@ const { iconText } = require('./common');
 // Add comment
 hexo.extend.filter.register('theme_inject', injects => {
   const config = hexo.theme.config.changyan;
-  if (!config.enable || !config.appid || !config.appkey) return;
+  if (!config || !config.enable || !config.appid || !config.appkey) return;
 
   injects.comment.raw('changyan', '<div class="comments" id="SOHUCS" sid="{{ gitalk_md5(page.path) }}"></div>', {}, {});
 
@@ -19,7 +19,7 @@ hexo.extend.filter.register('theme_inject', injects => {
 // Add post_meta
 hexo.extend.filter.register('theme_inject', injects => {
   const config = hexo.theme.config.changyan;
-  if (!config.enable || !config.count || !config.appid || !config.appkey) return;
+  if (!config || !config.enable || !config.count || !config.appid || !config.appkey) return;
 
   injects.postMeta.raw('changyan', `
   {% if post.comments %}

scripts/filters/minify.js

@@ -68,7 +68,7 @@ hexo.extend.filter.register('after_generate', () => {
   }
 
   // Comments
-  if (!theme.changyan.enable || !theme.changyan.appid || !theme.changyan.appkey) {
+  if (!theme.changyan || !theme.changyan.enable || !theme.changyan.appid || !theme.changyan.appkey) {
     hexo.route.remove('js/third-party/comments/changyan.js');
   }