Cannot Delete Loaded TileSets (aka Material)

[pixelinkmedia]

I cannot figure out how to remove a loaded Tileset Image (aka a material) from the Sprytile panel.
STEPS

1. Load a tileset
2. Create or Paint tile geometry. (optional)
3. Select a tile set to remove.
4. Click on "-" button... NOTHING happens

STEPS TO GET IT DELETED (which fails)

1. Go into object mode, select object
2. Got to material property... remove materal (tileset)
3. Go back into Sprytile.... still there
4. Go into outliner under oprhaned data.... remove it from there by Purging
5. Go back into Sprytile, now it says "invalid Object"

I then saved file, close Blender, restart and go back into Sprytile... "Invalid Data" still there.

The ONLY WAY to get rid of all traces of tileset is to actually delete the object mesh itself.
This of course means I have to remake the entire Object and retile again.
Not Ideal.... This seems like a BUG to me.

Trying to delete through Sprytile panel:

After purging data completely:

[MadleyLight]

I did figure this out if your still using it. You need to go to Sprytile Utilities and select new shadeless material. It should keep all the textures you as still using.

[dacanizares]

1. Remove material slot:
   

2. Validate tile grids:
   

Repeat setp 1 on each scene object (in case that you have multiple ones).