More Activity-based reasoning for saveActivity in Notice

If we can, get the activity ID from the activity itself, instead of the
supplied $options array.

lib/activity.php

@@ -244,6 +244,9 @@ class Activity
 
         if (!empty($targetEl)) {
             $this->target = new ActivityObject($targetEl);
+        } elseif (ActivityUtils::compareTypes($this->verb, array(ActivityVerb::FAVORITE))) {
+            // StatusNet didn't send a 'target' for their Favorite atom entries
+            $this->target = clone($this->objects[0]);
         }
 
         $this->summary = ActivityUtils::childContent($entry, 'summary');