Shared activities were missing the actor

plugins/Share/SharePlugin.php

@@ -162,6 +162,7 @@ class SharePlugin extends ActivityVerbHandlerPlugin
     {
         // TODO: How to handle repeats of deleted notices?
         $target = Notice::getByID($stored->repeat_of);
+        $act->actor = $target->getProfile()->asActivityObject();
         // TRANS: A repeat activity's title. %1$s is repeater's nickname
         //        and %2$s is the repeated user's nickname.
         $act->title = sprintf(_('%1$s repeated a notice by %2$s'),