fix(povray): quote an argument properly

Author: akinomyoga

completions/povray

@@ -43,7 +43,7 @@ _comp_cmd_povray()
             done
             cur="${povcur#[-+]O}" # to confuse _comp_compgen_filedir
             pfx="${povcur%"$cur"}"
-            _comp_compgen -a filedir $oext
+            _comp_compgen -a filedir "$oext"
             ((${#COMPREPLY[@]})) &&
                 _comp_compgen -Rv COMPREPLY -- -P "$pfx" -W '"${COMPREPLY[@]}"'
             return