fixed lava flow check

lava_flow_fixed

# fixed way
    def check_for_flow(self):
      if self.terrain_type == 'grass':
        return False

      neighbors = engine.metagrid.get_neighbors(self.pos)
      flow_dirs = []

      for direction in ORDINALS:
        these_neighbors = neighbors.get(direction) or {}
        ground_neighbor = these_neighbors.get(LAYER_GROUND)
        block_neighbor = these_neighbors.get(LAYER_BLOCKS)
        flow_this_dir = False
        if ground_neighbor and\
           ground_neighbor.terrain_type == 'grass' and\
           (ground_neighbor.land_height < self.land_height or\
            ground_neighbor.land_height <= engine.game.lava_height): 
          # there is a neighbor next to you, you can pour into them
          if not block_neighbor: 
            flow_this_dir = True
          elif not isinstance(block_neighbor, LavaStopper):
            flow_this_dir = True
            # you can flow!
            # kill any player on top
            if isinstance(block_neighbor, Player):
              block_neighbor.freeze_from_lava()
            elif isinstance(block_neighbor, Flammable):
              block_neighbor.die()

          if flow_this_dir: 
            if engine.game.stage == 'receding':
              self.terrain_type = 'grass'
              self.update_tex()
            ground_neighbor.handle_lava_flow()
            flow_dirs.append(direction)

      return flow_dirs