fixed the reference of `drag_selection` setting error.
fixed the reference of `drag_selection` setting error.

ninvfeng/jstree,500tech/jstree,iCasa/jstree,gustavobg/jstree,opencmii/jstree,ninvfeng/jstree,Project-TF/jstree,JuseChen/jstree,beealone/jstree,jacksonpradolima/jstree,500tech/jstree,Aliccer/jstree,Aliccer/jstree,ninvfeng/jstree,opencmii/jstree,Contagious06/jstree,Aliccer/jstree,duzun/jstree,opencmii/jstree,sadfuzzy/jstree,samokspv/jstree,neogis-de/jstree,JuseChen/jstree,codio/jstree,jacksonpradolima/jstree,aihua/jstree,iCasa/jstree,aihua/jstree,Contagious06/jstree,beealone/jstree,samokspv/jstree,gustavobg/jstree,500tech/jstree,neogis-de/jstree,aihua/jstree,gustavobg/jstree,iCasa/jstree,sadfuzzy/jstree,duzun/jstree,jacksonpradolima/jstree,vakata/jstree,beealone/jstree,Contagious06/jstree,neogis-de/jstree,Project-TF/jstree,sadfuzzy/jstree,JuseChen/jstree,codio/jstree,samokspv/jstree,vakata/jstree