Function delete_files has a bug

Hi,
into file /system/helpers/file_helper on line 143 the code check if the "filename" start not with dot but if it is a "directory", and not a file, it's a problem on line 149.

I found this bug about cache dir and someone tried to open a url like http://url/.somethings/xxx

I have fixed quickly with a rules on route but probably is more correct fix the CI file.

Another suggestion?