Azuremyst Isle - Tree's Company quest disguise allows to cast spell and bug the quest

• Quest: http://wotlk.openwow.com/quest=9531
• Disquise: http://wotlk.openwow.com/item=23792
• Tree disguise allows players to cast spell. So it is possible to kill hostile goblin NPC (http://wotlk.openwow.com/npc=17318) that should participate in scripted event with gnome npc (http://wotlk.openwow.com/npc=17243). After goblin’s death event stops, gnome does not disappear.
• I believe player should be stunned during this event, unable to do anything. Or the goblin should be unattackable.