add placeholder and fix mailer

src/server/util/mailer.js

@@ -93,7 +93,7 @@ module.exports = function(crowi) {
     return mc;
   }
 
-  function send(config, callback) {
+  function send(config, callback = () => {}) {
     if (mailer) {
       const templateVars = config.vars || {};
       return swig.renderFile(

src/server/views/admin/global-notification-detail.html

@@ -71,7 +71,7 @@
               </div>
 
               <div class="form-group notify-to-option {% if setting.__t != 'mail' %}d-none{% endif %}" id="mail-input">
-                <input class="form-control" type="text" name="notificationGlobal[toEmail]" value="{{ setting.toEmail || '' }}">
+                <input class="form-control" type="text" name="notificationGlobal[toEmail]" placeholder="Email" value="{{ setting.toEmail || '' }}">
                 <p class="help">
                   <b>Hint: </b>
                   <a href="https://ifttt.com/create" target="_blank">{{ t('notification_setting.email.ifttt_link') }} <i class="icon-share-alt"></i></a>
@@ -79,7 +79,7 @@
               </div>
 
               <div class="form-group notify-to-option {% if setting.__t != 'slack' %}d-none{% endif %}" id="slack-input">
-                <input class="form-control" type="text" name="notificationGlobal[slackChannels]" value="{{ setting.slackChannels || '' }}">
+                <input class="form-control" type="text" name="notificationGlobal[slackChannels]" placeholder="Slack Channel" value="{{ setting.slackChannels || '' }}">
               </div>
             </fieldset>