Path returned at None crash

[raczynskid]

a* algorythm returns None if no path can be found causing a crash

Traceback (most recent call last):
  File "D:/Python/rts/__main__.py", line 139, in <module>
    EM.set_group_target(MG, target_square)
  File "D:\Python\rts\game_libs\entity_manager.py", line 67, in set_group_target
    pixel_path = [mg.get_pixel_coords_by_row_column(node) for node in path]
TypeError: 'NoneType' object is not iterable