Repeated A* path generation

Hi,

I noticed none of the examples show case this but if you don't call AStar::getInstance().clear() between repeated path generation then for some reason it just always generates a wrong path after the first pathFinder.findPath() call. I didn't look into the internals of why, but I noticed that when generating different paths over and over you would get a correct path then after that it sort of generates what it feels like.