Make sure isUrl is only called with strings.
Make sure isUrl is only called with strings.

Anything else, is obviously not a url. Fixes GH-2211

ifduyue/sentry,beeftornado/sentry,mvaled/sentry,beeftornado/sentry,gencer/sentry,JamesMura/sentry,mvaled/sentry,gencer/sentry,beeftornado/sentry,mvaled/sentry,looker/sentry,ifduyue/sentry,looker/sentry,fotinakis/sentry,ifduyue/sentry,fotinakis/sentry,BuildingLink/sentry,looker/sentry,jean/sentry,fotinakis/sentry,JamesMura/sentry,alexm92/sentry,zenefits/sentry,daevaorn/sentry,jean/sentry,fotinakis/sentry,zenefits/sentry,nicholasserra/sentry,alexm92/sentry,JackDanger/sentry,JamesMura/sentry,jean/sentry,gencer/sentry,JackDanger/sentry,mvaled/sentry,zenefits/sentry,ifduyue/sentry,JackDanger/sentry,jean/sentry,nicholasserra/sentry,nicholasserra/sentry,jean/sentry,daevaorn/sentry,gencer/sentry,ifduyue/sentry,BuildingLink/sentry,looker/sentry,mitsuhiko/sentry,mitsuhiko/sentry,daevaorn/sentry,mvaled/sentry,daevaorn/sentry,JamesMura/sentry,zenefits/sentry,looker/sentry,BuildingLink/sentry,JamesMura/sentry,zenefits/sentry,gencer/sentry,BuildingLink/sentry,mvaled/sentry,BuildingLink/sentry,alexm92/sentry