Hotfix/175 file npe

I was in doubt if the SO reports as the file **exists**, but not readable `(.canRead) == false` when you have don't rights, .e.g

````clojure
user=> (-> "/root/.bash_history" (File.) (.exists))
;; => false

user=> (-> "/root/.bash_history" (File.) (.canRead))
;; => false
`````