do-directory crashes process when "." is passed as a directory argument

[robdaemon]

In the following code, you get a crash if you attempt to use "." as a pathname to the second argument to do-directory:

define function main (name :: <string>, arguments :: <vector>)
  local method print-entry (dir :: <pathname>, filename :: <string>, type :: <file-type>)
          format-out("%s\n", filename);
        end;

  do-directory(print-entry, ".");

  exit-application(0);
end function main;

main(application-name(), application-arguments());

Crash:

No applicable method, applying {<sealed-generic-function>: do-directory} to {<simple-object-vector>: {<simple-closure-method>: ??? ({<union>: <string>, <file-system-locator>}, <string>, {<union>: {<union>: #"file", #"directory"}, #"link"})}, #f}.
No applicable method, applying {<sealed-generic-function> 0x4e8038} to #[{function  0xb3110}, #f].
Breaking into debugger.
[1]    43966 trace trap  ./_build/bin/do-dir-test

Expected: this should work, and use the current working directory.

Replacing "." with working-directory() does work.