Fix `e is undefined`.
Fix `e is undefined`.

btmills/acorn,happibum/acorn,mysticatea/acorn,MarcelGerber/acorn,happibum/acorn,marijnh/acorn,ajaxorg/acorn,Rich-Harris/acorn,mathiasbynens/acorn,TimothyGu/acorn,ternjs/acorn,ternjs/acorn,mathiasbynens/acorn,btmills/acorn,ajaxorg/acorn,MarcelGerber/acorn,btmills/acorn,marijnh/acorn,marijnh/acorn,mysticatea/acorn,TimothyGu/acorn,Rich-Harris/acorn,mysticatea/acorn,ternjs/acorn,TimothyGu/acorn,mathiasbynens/acorn,happibum/acorn,MarcelGerber/acorn,ajaxorg/acorn,Rich-Harris/acorn