Add /api/v1/notifications/clear, non-existing link cards for statuses will

now return empty hash instead of throwing a 404 error. When following,
merge into timeline will filter statuses

app/controllers/api/v1/notifications_controller.rb

@@ -24,4 +24,9 @@ class Api::V1::NotificationsController < ApiController
   def show
     @notification = Notification.where(account: current_account).find(params[:id])
   end
+
+  def clear
+    Notification.where(account: current_account).delete_all
+    render_empty
+  end
 end

app/controllers/api/v1/statuses_controller.rb

@@ -22,7 +22,8 @@ class Api::V1::StatusesController < ApiController
   end
 
   def card
-    @card = PreviewCard.find_by!(status: @status)
+    @card = PreviewCard.find_by(status: @status)
+    render_empty if @card.nil?
   end
 
   def reblogged_by