Fixed crash.

activitypub.c

@@ -90,10 +90,11 @@ int timeline_request(snac *snac, char *id, char *referrer)
             status = activitypub_request(snac, id, &object);
 
             if (valid_status(status)) {
-                char *actor = xs_dict_get(object, "actor");
+                char *actor = xs_dict_get(object, "attributedTo");
 
                 /* request (and drop) the actor for this entry */
-                actor_request(snac, actor, NULL);
+                if (!xs_is_null(actor))
+                    actor_request(snac, actor, NULL);
 
                 /* does it have an ancestor? */
                 char *in_reply_to = xs_dict_get(object, "inReplyTo");