fix(filedir): work around bash-4.2 compgen -f -- "''"

Author: akinomyoga

bash_completion

@@ -1024,6 +1024,9 @@ _comp_compgen_filedir()
         local _quoted=$ret
         _comp_unlocal ret
 
+        # work around bash-4.2 where compgen -f "''" produces nothing.
+        [[ $_quoted == "''" ]] && _quoted=""
+
         # Munge xspec to contain uppercase version too
         # https://lists.gnu.org/archive/html/bug-bash/2010-09/msg00036.html
         # news://news.gmane.io/4C940E1C.1010304@case.edu