Error staging submodule removal when empty directory present

I'm having a hard time understanding why ``git stash save" chokes on a
submodule removal when an empty directory is present at the removed
submodule's path. If the submodule is staged for deletion, why not
just leave the empty directory alone?

The following Gist illustrates the situation I am encountering, and
includes OS information, Git version (2.3.5), and GIT_TRACE output:
https://gist.github.com/jawshooah/d60ff70952cff18099d7

Relevant post in the git-users Google Group, where I was encouraged to
query the mailing list:
https://groups.google.com/forum/#!topic/git-users/3YxxpVVXtqg

Thanks,
Josh