Fix found V8 deopt.
Fix found V8 deopt.

Increases perf from 230K to 360K lines/sec on std bench on my machine.

marcominetti/acorn-babel,claudiopro/babel,existentialism/babel,Rich-Harris/acorn,PolymerLabs/babel,Skillupco/babel,xiemaisi/acorn,happibum/acorn,maurobringolf/babel,btmills/acorn,gratex/acorn,mysticatea/acorn,maurobringolf/babel,happibum/acorn,jridgewell/babel,guybedford/babel,jridgewell/babel,ajaxorg/acorn,hzoo/babel,claudiopro/babel,mathiasbynens/acorn,ternjs/acorn,mysticatea/acorn,ajaxorg/acorn,guybedford/babel,maurobringolf/babel,marijnh/acorn,samwgoldman/babel,mathiasbynens/acorn,gratex/acorn,vadzim/babel,hulkish/babel,xiemaisi/acorn,kaicataldo/babel,marijnh/acorn,chicoxyzzy/babel,kaicataldo/babel,happibum/acorn,kellyselden/babel,chicoxyzzy/babel,ajaxorg/acorn,babel/babel,Rich-Harris/acorn,marcominetti/acorn-babel,marijnh/acorn,shuhei/babel,hzoo/babel,hulkish/babel,chicoxyzzy/babel,babel/babel,existentialism/babel,recipesjs/ingredients,samwgoldman/babel,jridgewell/babel,ternjs/acorn,shuhei/babel,gratex/acorn,MarcelGerber/acorn,btmills/acorn,PolymerLabs/babel,Skillupco/babel,btmills/acorn,wcjohnson/babylon-lightscript,TimothyGu/acorn,Skillupco/babel,hulkish/babel,guybedford/babel,kellyselden/babel,Rich-Harris/acorn,MarcelGerber/acorn,vadzim/babel,cbishopvelti/babylon,babel/babel,xiemaisi/acorn,samwgoldman/babel,hulkish/babel,kaicataldo/babel,chicoxyzzy/babel,Skillupco/babel,kellyselden/babel,danez/babylon,claudiopro/babel,mathiasbynens/acorn,kellyselden/babel,babel/babel,TimothyGu/acorn,PolymerLabs/babel,jridgewell/babel,hzoo/babel,mysticatea/acorn,lightscript/babylon-lightscript,shuhei/babel,hzoo/babel,ternjs/acorn,existentialism/babel,babel/babylon,kaicataldo/babel,marcominetti/acorn-babel,MarcelGerber/acorn,TimothyGu/acorn