fix compile test case in IE
fix compile test case in IE

seedalpha/vue,shupan123/vue-fixed-type,diermengdierme/vue,seedalpha/vue,fergaldoyle/vue,fergaldoyle/vue,th0r/vue,diermengdierme/vue,lepture/vue,karevn/vue,Endika/vue,diermengdierme/vue,galenyuan/vue,karevn/vue,galenyuan/vue,shupan123/vue-fixed-type,th0r/vue,galenyuan/vue,lepture/vue,lepture/vue,Endika/vue,fergaldoyle/vue,shupan123/vue-fixed-type,seedalpha/vue,th0r/vue,karevn/vue,Endika/vue