OK, after talking to some ArcMap people, I've learned you can't publish a map if it contains a basemap. So you simply need to remove the basmap and add it as a "regular" layer.
One question for you, however. Why are you trying to publish a basemap that is empty? What exactly are you trying to achieve? You can make any layer from ArcGIS Server "the basemap" when you add it to a web map. If that layer happens to be dynamic, the map will zoom dynamically, not from tiles. Depending on the extent of your area of interest, generating empty tiles for larger scales could yield a lot of tiles.
Thanks,
Mike