@Override protected void invalidated() {
                    if (null == get()) { set(""); }
                    fireTileEvent(VISIBILITY_EVENT);
                    fireTileEvent(REDRAW_EVENT);
                }
Sets the title of the tile. This title will only be visible
if it is not empty.

@param TITLE
src/main/java/eu/hansolo/tilesfx/Tile.java