Prevent false positives for 'untracked' empty directories.

Fixes a regression in #13

fish_prompt.fish

@@ -322,7 +322,7 @@ function __bobthefish_prompt_git -a current_dir -d 'Display the actual git state
   set -l new ''
   set -l show_untracked (git config --bool bash.showUntrackedFiles)
   if [ "$theme_display_git_untracked" != 'no' -a "$show_untracked" != 'false' ]
-    set new (command git ls-files --other --exclude-standard --directory)
+    set new (command git ls-files --other --exclude-standard --directory --no-empty-directory)
     if [ "$new" ]
       if [ "$theme_avoid_ambiguous_glyphs" = 'yes' ]
         set new '...'