fix multi-select test case bug detection in IE9
fix multi-select test case bug detection in IE9

greennyreborn/vue,KingMario/vue,Ddder-FE/vue,Kingwl/vue,vuejs/vue,greennyreborn/vue,Jinjiang/vue,KingMario/vue,Jinjiang/vue,xueyaodeai/vue,Kingwl/vue,leemotive/vue,Jinjiang/vue,vuejs/vue,xueyaodeai/vue,KingMario/vue,xueyaodeai/vue,lizhiyao/vue,Jinjiang/vue,optimizely/vue,greennyreborn/vue,cnchanning/vue,Ddder-FE/vue,lizhiyao/vue,cnchanning/vue,Kingwl/vue,Hanks10100/vue,leemotive/vue,KingMario/vue,xueyaodeai/vue,leemotive/vue,lizhiyao/vue,vuejs/vue,Hanks10100/vue,Kingwl/vue,greennyreborn/vue,lizhiyao/vue,vuejs/vue,leemotive/vue,cnchanning/vue,Ddder-FE/vue,Hanks10100/vue,Hanks10100/vue,Ddder-FE/vue