Print error if index value in a page is wrong type
Print error if index value in a page is wrong type

This was causing a panic with no information displayed about the
page causing the error.

kujohn/hugo,gohugoio/hugo,digitalcraftsman/hugo,coderzh/hugo,Zenithar/hugo,fedelibre/hugo,gohugoio/hugo,tjyang/hugo,tubo028/hugo,halostatue/hugo,ifraixedes/hugo,badoet/hugo,bogem/hugo,tischda/hugo,tatsushid/hugo,mitchchn/hugo,ffrizzo/hugo,MarkDBlackwell/hugo,digitalcraftsman/hugo,mayah/hugo,mdhender/hugo,tubo028/hugo,vbatoufflet/hugo,sprig/hugo,tischda/hugo,badoet/hugo,jygastaud/hugo,soundrussian/hugo,mayah/hugo,abourget/hugo,gohugoio/hugo,abourget/hugo,ifraixedes/hugo,ffrizzo/hugo,anthonyfok/hugo,tjyang/hugo,coderzh/hugo,vbatoufflet/hugo,bramp/hugo,MarkDBlackwell/hugo,jygastaud/hugo,bramp/hugo,halostatue/hugo,tatsushid/hugo,fedelibre/hugo,mitchchn/hugo,anthonyfok/hugo,soundrussian/hugo,bogem/hugo,derekperkins/hugo,melo/hugo,kujohn/hugo,ryanclarke/hugo,mdhender/hugo,sprig/hugo,mdhender/hugo,anthonyfok/hugo,Zenithar/hugo,fedelibre/hugo,derekperkins/hugo,ryanclarke/hugo,fhergomez/hugo,mdhender/hugo,fedelibre/hugo,fhergomez/hugo,melo/hugo