fix style merging assertion in IE
fix style merging assertion in IE

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