Export Contains Junk Data

When my artist exports the tile map data with multiple layers, any unmapped tiles are still written to the output file. I figure this is an oversight since I cannot think of any reason why you would want to parse an invalid tile ID (unmapped tiles export as tile ID -1); it creates the potential for bugs, bloats file size, and increases parse time.
Could you update the tile map exporter to ignore unmapped tiles?
Could you update the tile map exporter to ignore unmapped tiles?