Merge branch 'hotfix/activity-without-content' into 'develop'

Twitter ActivityView: fix crash with activity without content

See merge request pleroma/pleroma!572

lib/pleroma/web/twitter_api/views/activity_view.ex

@@ -245,9 +245,11 @@ def render(
       |> Formatter.emojify(object["emoji"])
 
     text =
+      if content do
         content
         |> String.replace(~r/<br\s?\/?>/, "\n")
         |> HTML.strip_tags()
+      end
 
     reply_parent = Activity.get_in_reply_to_activity(activity)