msi: Don't set the shortcut's working directory if it's NULL.

[Dan Kegel]

On 7/27/06, Mike McCormack <mike at codeweavers.com> wrote:
> ---
>   dlls/msi/action.c |    3 ++-
>   1 files changed, 2 insertions(+), 1 deletions(-)

That fixes the last AA installer crash.   As soon as that's committed we
can close out http://bugs.winehq.org/show_bug.cgi?id=5139

Thanks!!
- Dan