add error handling in vm.$get (fix #781)
add error handling in vm.$get (fix #781)

KuroGuo/vue,haner199401/vue,Jonavin/vue,PUSEN/vue,knownasilya/vue,Suixinlei/vue,Erane/vue,meiwenhui/vue,15521316173/vue,Zeratul5/vue,longjl/vue,Zeratul5/vue,AtChina/vue,seedalpha/vue,yuche/vue,diermengdierme/vue,WQuanfeng/vue,echoZQ/vue,macroxing/vue,lovewitty/vue,Iamlars/vue,th0r/vue,karevn/vue,VictorChaun/vue,diermengdierme/vue,gxr1020/vue,15521316173/vue,bsn069/vue,zOxta/vue,rohmad-st/vue,PUSEN/vue,endaaman/vue,Endika/vue,Alen-gao/vue,squallyan/vue,endaaman/vue,r14r/fork_javascript_vue,VimVincent/vue,fergaldoyle/vue,elvinzhu/vue,cuhuak/vue,WQuanfeng/vue,bsn069/vue,Endika/vue,VimVincent/vue,cnbin/vue,jRoadie/vue,noyobo/vue,likaiwalkman/vue,wangjun/vue,cgvarela/vue,zsh2938/vue,seedalpha/vue,cuhuak/vue,ke-pan/vue,ke-pan/vue,kazupon/vue,fergaldoyle/vue,JsAaron/vue,Iamlars/vue,VictorChaun/vue,jhaesus/vue,cgvarela/vue,cnbin/vue,lepture/vue,meiwenhui/vue,jwdeitch/vue,yuByte/vue,wangjun/vue,yuByte/vue,loki315zx/vue,JosephSilber/vue,lovewitty/vue,jwdeitch/vue,seedalpha/vue,galenyuan/vue,lishengzxc/vue,coopsource/vue,longjl/vue,JsAaron/vue,gold3bear/vue,KuroGuo/vue,lepture/vue,kazupon/vue,cheapsteak/vue,macroxing/vue,th0r/vue,diermengdierme/vue,loki315zx/vue,elvinzhu/vue,galenyuan/vue,gxr1020/vue,prosenjit-itobuz/vue,zsh2938/vue,GloriaCHL/vue,lazarofl/vue,Erane/vue,jhaesus/vue,squallyan/vue,gold3bear/vue,prosenjit-itobuz/vue,lishengzxc/vue,zOxta/vue,Suixinlei/vue,beni55/vue,karevn/vue,haner199401/vue,yuche/vue,lazarofl/vue,knownasilya/vue,GloriaCHL/vue,echoZQ/vue,AtChina/vue,lepture/vue,meleslilijing/vue,shupan123/vue-fixed-type,noyobo/vue,shupan123/vue-fixed-type,meleslilijing/vue,karevn/vue,Endika/vue,coopsource/vue,galenyuan/vue,rohmad-st/vue,shupan123/vue-fixed-type,fergaldoyle/vue,th0r/vue,Alen-gao/vue,beni55/vue,r14r/fork_javascript_vue,likaiwalkman/vue,JosephSilber/vue,jRoadie/vue,cheapsteak/vue,Jonavin/vue