Guard against trying to read args from a shell function object in def.js
Guard against trying to read args from a shell function object in def.js

Closes #238

jgiles/tern,eranif/tern,messfairy/tern,neoclide/tern,rustemferreira/tern,inafact/tern,kentdoppelganger/tern,emacsmirror/tern,eranif/tern,MarcelGerber/tern,emallson/tern,ternjs/tern,othree/tern,dorellang/tern,adrianton3/tern,talyian/tern,anandthakker/tern,jgiles/tern,rustemferreira/tern,cloud9ide/tern,cdosborn/tern,fileability/tern,othree/tern,rustemferreira/tern,pombredanne/tern,mcanthony/tern,eranif/tern,ternjs/tern,messfairy/tern,neoclide/tern,talyian/tern,emallson/tern,albertinad/tern,angelozerr/tern,emallson/tern,jgiles/tern,mcanthony/tern,emacsmirror/tern,othree/tern,Icenium/tern,emacsmirror/tern,marijnh/tern,talyian/tern,MarcelGerber/tern,anandthakker/tern,neoclide/tern,ypresto/tern,Icenium/tern,jason0x43/tern,sqs/tern,fileability/tern,adrianton3/tern,albertinad/tern,Icenium/tern,cloud9ide/tern,mcanthony/tern,anandthakker/tern,MarcelGerber/tern,OliverJAsh/tern,dorellang/tern,angelozerr/tern,messfairy/tern,vegansk/tern,albertinad/tern,ternjs/tern,kylehg/tern,cdosborn/tern,marijnh/tern,cdosborn/tern,fileability/tern,adrianton3/tern,dorellang/tern,marijnh/tern