Fixed bug in Editor where one could click outside the tile sprite sheet
during tile selection and get a tile id that was out of range and place
it in the world. Depending on the type (Scene, Solid, Thru) it would act
like an invisible version of that tile type
Additionally, added a sanity check where if a tile realises its id cant
map to a valid graphic, it prints an error message. Need to move
logs/errors from System.out.println() to something else eventually.
Added eraser capabilities: Goodies and tiles can now be erased. The
internal implementation allows for a feature that I think I want to
keep: Overlapping goodies on tiles. An editor feature to prevent adding
solids to goodie tiles and vice-versa is important, but perhaps allowing
them to be overlayed on scenes/thrus would be nice.