Fix type inference for unsyntactic regexps
Fix type inference for unsyntactic regexps

They get a .value of undefined, which would confuse literalType

Issue #447

marijnh/tern,eranif/tern,jgiles/tern,albertinad/tern,anandthakker/tern,emacsmirror/tern,cdosborn/tern,emallson/tern,MarcelGerber/tern,rustemferreira/tern,MarcelGerber/tern,Icenium/tern,messfairy/tern,othree/tern,mcanthony/tern,othree/tern,ternjs/tern,fileability/tern,eranif/tern,anandthakker/tern,fileability/tern,mcanthony/tern,marijnh/tern,ternjs/tern,albertinad/tern,eranif/tern,talyian/tern,dorellang/tern,Icenium/tern,dorellang/tern,fileability/tern,emallson/tern,emallson/tern,MarcelGerber/tern,talyian/tern,othree/tern,emacsmirror/tern,cdosborn/tern,talyian/tern,neoclide/tern,marijnh/tern,cdosborn/tern,albertinad/tern,messfairy/tern,adrianton3/tern,mcanthony/tern,dorellang/tern,neoclide/tern,emacsmirror/tern,anandthakker/tern,jgiles/tern,adrianton3/tern,rustemferreira/tern,jgiles/tern,adrianton3/tern,messfairy/tern,Icenium/tern,rustemferreira/tern,neoclide/tern,ternjs/tern