Fixes dashboard sorting

Closes #681 (closed)

What does this MR do?

The dashboard sorting failes when there are events (Termine) in it since they don't have a time attribute. This leads to an exception and thus prevents the further execution of the sort function. The current state is as follows: the events get listed on top. In the dashboard activity they are not shown. This behavior does not change by this fix but it will fix the sorting of the page.

How confident are you it won't break things if deployed?

See the screenshots:

Links to related issues

Checklist

• added a test, or explain why one is not needed/possible...
• no unrelated changes
• asked someone for a code review
• joined #foodsharing-beta channel at https://slackin.yunity.org
• added an entry to CHANGELOG.md (description, merge request link, username(s))

client/src/activity.js

@@ -93,11 +93,13 @@ const activity = {
   append: function (up) {
     var quickreply = ''
 
-    if (up.quickreply != undefined) {
+    if (up.quickreply !== undefined) {
       quickreply = `<span class="qr"><img src="${activity.user.avatar}" /><textarea data-load="0" data-url="${up.quickreply}" name="quickreply" class="quickreply noninit" placeholder="Schreibe eine Antwort..."></textarea><span class="loader" style="display:none;"><i class="fas fa-spinner fa-spin"></i></span></span>`
     }
 
-    activity.$container.append(`<li data-ts="${up.time}"><span class="i"><img width="50" src="${up.icon}" /></span><span class="n">${up.title}</span><span class="t">${up.desc}</span>${quickreply}<span class="time"><i class="far fa-clock"></i> ${$.timeago(up.time)} <i class="fas fa-angle-right"></i> ${timeformat.nice(up.time)}</span><span class="c"></span></li>`)
+    if (up.time !== null) {
+      activity.$container.append(`<li data-ts="${up.time}"><span class="i"><img width="50" src="${up.icon}" /></span><span class="n">${up.title}</span><span class="t">${up.desc}</span>${quickreply}<span class="time"><i class="far fa-clock"></i> ${$.timeago(up.time)} <i class="fas fa-angle-right"></i> ${timeformat.nice(up.time)}</span><span class="c"></span></li>`)
+    }
   },
 
   initQuickreply: function () {